The Effectiveness of a Technology-Based Isometrical Transformation Flipped Classroom Learning Strategy in Improving Students’ Higher Order Thinking Skills

Isometric Transformation is one of the essential topics in the Malaysian Secondary School Mathematics Curriculum. In general, Malaysia’s achievements in Trends in International Mathematics and Science Study (TIMSS) and Program for International Student Assessment (PISA) were found to be less encouraging, especially in the field of Geometry. This fact clearly implies that the mastery of Higher-Order Thinking Skills (HOTS) of Malaysian students is still low, especially in the topic of Isometric Transformation. Therefore, this study was conducted to develop Flipped Classroom Learning Strategy (FCLS) activities and evaluate their effectiveness in increasing Malaysian secondary school students’ HOTS in Isometric Transformation. This study was conducted in two stages whereby the first stage involved the development of FCLS activities, while the second stage was run to evaluate the effectiveness of FCLS activities in enhancing students’ HOTS for the topic of Isometric Transformation. The development of activities involved three phases. The first phase was the needs analysis phase which involved a preliminary survey towards students’ learning difficulties at each level of HOTS in the topic of Isometric Transformation. The second phase was the design and development stage of FCLS activities, involving the learning activities inside and outside the classroom in line with the topic of Isometric Transformation. The last phase was the evaluation phase which involved the content validation and evaluation on the suitability of FCLS activities by 11 experts. Next, the second stage was a quasi-experimental design which involved 131 Form 2 students from two secondary schools in Johor. The study sample was divided into two groups which were the treatment group and the control group. The study was conducted over eight weeks. Mann-Whitney test results showed a significant difference (p =.000 <.05) in the overall level and also for all of the four levels of HOTS for both control and treatment groups. The results of this study showed that the teaching and learning process that used FCLS activities successfully created an effective learning situation in improving students’ HOTS in the topic of Isometric Transformation. In conclusion, these FCLS activities should be used as guidelines for educators to increase HOTS in mathematics education.

INDEX TERMS Flipped classroom, higher order thinking skills (HOTS), isometric transformation.

I. INTRODUCTION
Education is one of the platforms that can cultivate higher order thinking skills (HOTS) and 21st century learning skills [1]. HOTS is a concept that emphasizes critical thinking skills rather than rote memorization. One of the most popular HOTS taxonomies of learning was introduced by Bloom 1956 which included knowledge, comprehension, application, analysis synthesis and evaluation. However, in 2001, the revised Bloom's Taxonomy was introduced by Anderson and Krathwohl. The top three thinking skills in the Bloom Taxonomy involved critical or higher-order thinking skills. HOTS plays an important role in developing human capital that can compete at the global level [2]. In this regard, many countries such as the United States [3], South Korea [4], [5], Singapore [6] have prioritized HOTS in their education systems including Malaysia. In order to foster and empower HOTS, the Malaysian Ministry of Education has launched the Malaysian Education Blueprint 2013-2025 that has been clearly incorporated in the learning standards for the Primary School Standard Curriculum and the Secondary School Standard Curriculum [7]. The Ministry of Education has adopted Anderson's revised edition of the Bloom Taxonomy hierarchy in the national education system and employed it as one of the important elements in the curriculum framework for all subjects including mathematics. This can help students master all levels of HOTS which refers to the skills of applying, analyzing, evaluating and creating. These skills are greatly emphasized in the Malaysian education system [2].
HOTS is the ability to apply knowledge, skills and values in reasoning and reflecting in order to solve problems, make decisions, innovate and create something [2]. This skill is also emphasized in mathematics subjects. It is important for students to master this skill that enables them to face challenges and take risks in trying new solution methods. However, these objectives will be difficult to achieve if students are unable to master mathematics subjects, especially in terms of solving HOTS problems. This is evident in the performance of Malaysian students in international assessments, such as Trends in International Mathematics and Science Study (TIMSS) and the Program for International Students Assessment (PISA), which show a less than satisfactory level [8]. Meanwhile, the poor performance of secondary school students in public examinations also lends evidence that the mastery of mathematics is still low in which many students are still unable to answer the mathematics questions [9]. This clearly shows that Malaysian students are weak in the mastery of the international and local HOTS assessments. Their performance, unfortunately, does not meet the Ministry of Education's targets. Therefore, efforts to cultivate and improve students' HOTS, especially in mathematics subjects, need to be given due attention.
HOTS in the teaching and learning process is critical in order to meet the demands of the National Philosophy of Education and the country's needs towards achieving the status of a high-income developed country [10]. The revolution in mathematics education is now also focusing on HOTS. However, previous studies show that HOTS among Malaysian students is still low in both international [11], [12] and national assessments [13]. This is evident in the declining pattern in the assessments of TIMSS 1999, TIMSS 2003, TIMSS 2007, PISA 2011 and PISA 2012 [14], [15], [16]. This finding is further reinforced by a needs study report by Consultants Kestrel Education (UK) and 21st Century Schools (USA) which found that the mastery of HOTS among Malaysian teachers and students is still low.
The low mastery of HOTS among students is due to the implementation of teachers' pedagogical practices [17]. In Malaysia, many teachers still use conventional teaching methods [18]. In addition, mathematics teachers are still struggling with good pedagogical practices for teaching HOTS [19], [20]. Teachers are also still confused about the use of specific keywords for the formulation of HOTS questions [8], as supported in [21] in which the authors claim that teachers are still at a moderate level in the application of HOTS since they are unable to plan questions, assignments and activities that require students to develop thinking skills. As a result, students' thinking has to be trained with open questions in order to understand new learning in mathematics [22]. Next, the students' low level of HOTS in mathematics is linked to their lack of knowledge to connect information in their daily life [23], [24], [25]. This includes students' difficulties in solving HOTS questions using a hands-on solution strategy, which is due to their poor grasp of basic mathematics knowledge [26], [27]. This problem occurs since students tend to memorize formulas without understanding concepts, theorems and formulas in mathematics. They also provide correct answers without using their existing knowledge and experience [28].
It can be concluded that Malaysian students are still at a low level of mastery of HOTS in mathematics, which is below the level expected by the Ministry of Education. Therefore, many studies have been conducted that aim to improve students' HOTS [22], [29]. However, these studies neglect the topic of Isometric Transformation. Therefore, the current study was conducted by considering the use of a flipped classroom learning strategy (FCLS) in order to increase students' HOTS for the topic of Isometric Transformation.

II. DIFFICULTY IN LEARNING ISOMETRIC TRANSFORMATIONS
Students' mastery on the concept of transformation geometry is important as it helps them in enhancing the analyzing and synthesizing skills as well as the problem-solving skills [30]. According to [31], learning geometry can provide opportunities for the students to develop their spatial visualization skills. In addition, learning geometry also can enhance reasoning and critical thinking skills among the students [32]. Thus, by understanding and mastering the concept of transformation geometry, the students can indirectly understand the other mathematical concepts.
Many researchers have focused on Isometric Transformation which is the eleventh topic based on the Form Two Mathematics Curriculum and Assessment Standard Document. This document prioritizes transformation, translation, reflection, rotation, isometry, congruence and rotational symmetry [2]. Isometric transformation is a topic that demands attention from relevant parties involved in the mathematics curriculum [33]. However, the 2015 TIMSS study report showed that only 30% of Form Two students in Malaysia were able to answer the symmetry and reflection concept questions correctly. This percentage is relatively low compared to the international average, which is 50.9%. This result proves that Malaysian students have not mastered the concept of symmetry and reflection. They are also unable to relate symmetry to everyday life [34]. Moreover, [35] support the above statement by stating that there is a substantial difference between students in Malaysia and those in Singapore in terms of their achievements in the geometric cognitive domain; Malaysian students are rarely exposed to open-ended questions as well as non-routine and hands-on exercises in the topic of Isometric Transformation [34].
Students' difficulties in answering HOTS questions for Isometric Transformation can be linked to their inability in obtaining mathematical information [36], [37]. This situation is due to difficult sub-topics that involve the exploration of translation, reflection, rotation, isometry, congruence, and rotational symmetry [38], [39]. It was found in previous studies that students are unsure about the exact terms for translation and rotation, including the drawing images of rotation that are inaccurate [40], [41], [42].
Students, therefore, need to apply HOTS in order to avoid misconceptions in the topic of Isometric Transformation [43]. Furthermore, students also experience problems especially when making generalizations about the transformation patterns associated with their daily life [44]. Although teachers guide students to transfer their knowledge to non-routine and real-life situations, students still face difficulties in relating the topics to their daily life situations [38]. This shows that it is critical to transfer the topic of Isometric Transformation into students' daily life so that they can understand the topic in greater depth [45]. Passive students usually show poor thinking skills during teaching and learning since they are reluctant to provide ideas during discussion activities and submissive to the suggestions from their group mates [46].
In conclusion, all the studies above show the difficulties experienced by students in the topic of Isometric Transformation [41], [47], [48]. One of the learning strategies that can be used to make it easier for students to understand this topic is the integration of technology and communication, which is through a flipped classroom by [49]. Through a technology-based flipped classroom, students can understand related topics in depth and relate such topics to their daily life.

III. FLIPPED CLASSROOM LEARNING STRATEGY (FCLS) IN MATHEMATICS CLASSROOM
In Malaysia, a flipped classroom is one of the pedagogical strategies that has been emphasized by the Ministry of Education in secondary schools [14]. Four pillars behind the flip learning in Malaysia are flexible environments, learning cultures, intentional contents, and professional educators. It was indicated in one recent study that the flexibility and versatility features of a flipped classroom made it widely diffused in the Malaysian classroom context [50]. According to [51], a flipped classroom method provides space and opportunities for students to learn at their own pace and encourages them for active learning.
Past studies show that the Flipped Classroom Learning Strategy (FCLS) has great potential to be implemented in mathematics education [52]. Among the advantages of this FCLS is that students can plan and evaluate the study period correctly [53]. Students can also plan their learning activity time by interacting with their peers outside and inside the classroom. This makes it easier for them to interact with their teachers if there is ambiguity about the concept [54]. Teachers will provide feedback so that students can address potential problems raised in the classroom. In this way, teachers can maximise their time in the classroom. Indirectly, students will build a collaborative network to help them improve their academic performance [55].
Through FCLS, students can also answer questions related to the topic and receive appropriate feedback in the form of quizzes submitted online before FCLS activities [56]. Students can also directly ask questions so that teachers are able to provide solutions. Therefore, FCLS based on information and communication technology will help teachers to be more prepared to face various questions and problems from their students [57].
According to [58], this learning strategy will enable students to apply HOTS and master mathematics concepts in the classroom. After learning mathematics using this FCLS, students will be more confident to solve mathematics HOTS questions [59]. However, there is limited research that examines the implementation of FCLS in mathematics including activities conducted before, during and after the teaching and learning process. This limitation is evident either internationally [60] or locally [61], [62], [63]. The initial study conducted by Mukherjee and Pillai [63] in Malaysia focused only on the implementation of FCLS in the higher education setting. The study shows that FCLS has potential benefits in knowledge development, collaborative learning and time-saving in the classroom [64]. However, the study does not detail out the level of implementation at the secondary school level. Subsequently, a quasi-experimental study was conducted by [65]; she suggested that the implementation of FCLS could be extended to regular high school students in order to see the impacts and constraints from other contexts. As a result, other researchers started to consider the gap in previous studies by developing FCLS activities for daily VOLUME 11, 2023 secondary school students and by looking at the impact of these activities in terms of HOTS' mastery

IV. THE POTENTIAL OF A FLIPPED CLASSROOM LEARNING STRATEGY (FCLS) TO IMPROVE STUDENTS' HIGHER ORDER THINKING SKILLS (HOTS) IN MATHEMATICS
A flipped classroom gives students the opportunity to have their own learning space and learning pace. In the conventional method, students may not be able to follow the speed of teachers' delivery which can reduce the amount of information delivered to students [66]. As a flipped classroom is parallel to the student-centered learning paradigm in which students are responsible for their learning process [67], students can manage and regulate their learning and thinking in a more effective manner. In addition, considering the fact that the high-level thinking process requires a lot of cognitive investments, the flexibility features of a flipped classroom can reduce the cognitive load faced by students.
Previous studies have shown that the activities using the flipped classroom learning strategy (FCLS) in teaching mathematics at secondary schools are still underexplored. According to [68], teachers need to give more attention to activities for FCLS. It turns out that most researchers do not detail out how to implement activities for FCLS in teaching and learning [69], leading to difficulties among teachers in implementing FCLS [70]. Therefore, this study aims to develop activities for FCLS as teaching aids that can be used by teachers in teaching and learning so that it is easier for students to understand and answer HOTS questions on the topic of Isometric Transformation. The FCLS activities were developed with complete implementation guidelines that aimed at helping to reduce problems and constraints among teachers. The theory of Social Constructivism by [71] was chosen as the underlying principle for the development of activities for FCLS. This theory of Social Constructivism was emphasized in all three phases, including those activities that focused on the students' HOTS, as found in the flipped classroom model by [72], which was also adapted in the objectives of the current study.
Each activity in FCLS was developed by the researchers according to the hierarchy of learning in the topic of Isometric Transformation as specified in the Standard Document of Curriculum and Assessment for Form Two Mathematics Curriculum [2]. The activities for FCLS were divided into several sub-headings and built sequentially so that these activities would be applied effectively inside and outside the classroom. The development of such activities would help teachers implement FCLS in the teaching and learning of mathematics in secondary schools in order to increase students' HOTS through the three phases of implementation.
In the first phase, which was the exploratory phase, the activities for FCLS would increase students' motivation by watching videos and additional reference materials to learn mathematics and stimulate the mastery of HOTS [59], [73]. The second phase, which was the phase of application, involved learning outside and inside the classroom in which the teachers could relate advanced knowledge about the concepts by answering various forms of mathematics HOTS questions [74]. Through FCLS activities, teachers could guide students in completing comprehensive exercises that involved the skills of applying, analyzing, evaluating and creating for each sub-topic in Isometric Transformation [75]. The variety of activities with group members would increase students' motivation and create a comfort zone for them [76].
The third phase was the reflection phase which required students to conduct self-reflection for the improvement of individual learning. With the help of FCLS activities, teachers could also improve the teaching and learning process [77], [78]. Indirectly, teachers could improve students' HOTS [22], [79]. This is in line with FCLS which has the potential to increase students' understanding, encourage their critical and creative thinking skills, and increase their achievement and motivation [59].

VI. RESEARCH METHODOLOGY
The design of this study was divided into two stages, namely (1) the design and development stage and (2) the effectiveness testing stage. The first stage focused on the development of products and hardware, i.e., the intended product for FCLS [80], [81]. The development of activities for FCLS employed the design principles of [82] model as a guide in building interactive and systematic teaching and learning activities. This model was chosen in the development of activities for FCLS in order to test and verify the theory in practice [83].
In the design and development stage, there were 11 experts involved in this study. In order to ensure that the activities developed were appropriate, two senior Mathematics lecturers, two excellent teachers and a Malaysian Secondary School Standard Curriculum Lead Trainer for Mathematics provided comments and feedback on the draft activities developed. The expert evaluation of the instruments and draft activities aimed to obtain an evaluation of the content validity of the items. Meanwhile, a language expert was also appointed to assess whether the language used was easy to understand by the students. After the confirmation of the draft activities for FCLS, the improvement process was carried out according to the comments and feedback from the experts.
Next, the improved draft was evaluated by five expert teachers. This step aimed to obtain an assessment of the content validity of the items as well as language appropriateness. After the confirmation of the draft activities based on the comments and feedback from the expert teachers, the improved draft was given to five Form Two students to be evaluated from the students' point of view. Based on the views and suggestions from the students, modifications were made to some sentence structures and terms in the research questionnaire.
In the context of this study, this model was compatible with the Social Constructivism Theory. This theory was applied in FCLS through teaching and learning activities that were expected to contribute to the cognitive development of students in an interactive and dynamic learning environment. In the activity development process, the researchers applied the activity construction steps suggested by [82] through three main phases, as shown in Fig. 1. Fig. 2 lists down activities in the three phases of learning based on the characteristics of the Social Constructivism Theory implemented in FCLS [72]. In developing the activities for FCLS, the researchers prioritized the three phases of learning, namely the exploration phase before learning, the application phase and strengthening of concepts during teaching and learning, and the reflection phase after teaching and learning [84]. Among the activities in the first phase were out-of-class learning that encouraged students' inquiry by watching videos and commenting, exploring the topic on their own, preparing with additional references, and answering online quiz questions [59]. Sending video links via WhatsApp allowed students to conduct investigations and find answers to problems given at the beginning of learning [85], [86]. This phase aimed to improve the nature of discovery among students. Students also needed to comment on videos in virtual chat rooms or forums so that they could communicate with other students or teachers about a specific concept. The purpose of this room was to allow students to exchange opinions, share knowledge and reflect after or during the learning mode [87]. Teachers could also ask questions that could stimulate students through online quizzes [88]. The second phase was particularly conducted to observe student-centered teaching and learning activities. Teachers could initiate teaching and learning in the classroom by making connections between topics presented in video links or quizzes. Students' views and answers could help teachers detect difficulties in the topic and avoid students' misconceptions [89]. Group learning activities could give students the opportunity to improve their weaknesses. Besides, training in the form of HOTS could give students the opportunity to master learning more deeply and to draw conclusions. This phase aimed to guide students to think outside the box in order to solve problems, express ideas and information confidently.
Finally, the reflection phase was conducted after class in which students provided feedback about the day's teaching and learning. Students also read additional materials on the topics learned, followed by hands-on activities such as projects so that knowledge could be applied in real situations. At the stage of selecting activities, media and teaching aids, VOLUME 11, 2023 the researchers arranged them based on [90], as shown in Table 1.

A. EFFECTIVENESS TESTING
The second stage was to test the effectiveness of activities for the FCLS that were built in improving students' HOTS in the topic of Isometric Transformation. A quasi-experimental design was used in this stage involving a pre-post Isometric Transformation HOTS test [91], [92]. A quasi-experimental design was suitable as the present study aimed to test the effectiveness of students' HOTS in the topic of Isometric Transformation. Moreover, [93] also support this design because of its strength. In this study, a quasi-experimental design was used for the treatment group who was involved in FCLS activities. Meanwhile, the control group underwent conventional learning with the help of textbooks, power point presentations, workbooks and worksheets. All learning activities for the control group took place in the classroom environment. This coincides in [94] in which the author states that the treatment group should receive a new treatment while the control group is maintained in the usual form. The two groups were given a pre-test and a post-test before and after the study was conducted, as shown in Table 2. Table 2 shows a quasi-experimental design that uses a non-equivalent group's pre-post-test design. This design was chosen because existing groups were used so as not to disturb the school's natural environment. The sample was equivalent in several aspects such as age, background, academic qualifications and existing knowledge [95]. The researchers selected a treatment group consisting of Form Two students at a secondary school; this group used FCLS activities in the topic of Isometric Transformation (X1). Meanwhile, the control group consisted of Form Two students at another secondary school; this group received conventional learning (X2). The treatment and control groups were chosen from different schools to avoid the threat of internal validity and subsequent invalidity in the results of the study.
In the first week, a pre-HOTS Isometric Transformation test was given to the treatment group (X1) and also the control group (X2). After the pre-test was conducted, the treatment group (X1) followed the activities for FCLS in the learning session starting in the second week for eight weeks. Meanwhile, the control group (X2) followed conventional learning for eight weeks. In the following week, the treatment group (X1) and the control group (X2) were given a post-HOTS Isometric Transformation test. The time period for the post-test was considered appropriate. According to [96], the appropriate period for conducting a post-test is within a period of one month, six months or a year after a pretest. This is recommended in order to minimize the internal validity of the study caused by the subjects' maturity factor. However, this quasi-experimental design was still exposed to some threats of validity and reliability [96]. To ensure that the findings of the study were due to treatment factors only, the researchers made efforts to control the threats to the validity of internal and external data before conducting the study [97].

B. ISOMETRIC TRANSFORMATION HOTS TEST
The Isometric Transformation HOTS test was conducted to identify the effectiveness of FCLS activities on HOTS' mastery in the topic of Isometric Transformation. The construction process of the HOTS mathematics items involved four stages: (1) preparing the Test Specification Table, (2) building the items in each construct, (3) sending the constructed items to a discussion session with the experienced teachers, and (4) sending the constructed instrument to experts for  validation. In the first stage, the researchers prepared a Test Specification Table based on the Form Two Mathematics Curriculum and Assessment Standard Document for the Isometric Transformation topic. This was to ensure that the test included items that measured various cognitive domains of students [98]. Next, the researchers also studied the existing HOTS Isometric Transformation items in the literature. The purpose was to examine the constructs and items that were previously built by other researchers so that they could be modified according to the context of the current study. Therefore, in the second stage, the researchers adapted some appropriate items from the HEBAT Module (Life, Exploration, Higher Level Thinking) for Mathematics Form Two published by the Curriculum Development Division (CDD), MOE in 2016 [2].
Next, the third stage was a discussion session with experienced teachers to obtain information, ideas and improvements for the construction of HOTS items. This was to further strengthen the items chosen for the Isometric Transformation HOTS test. The researchers also made refinements according to the recommendations given by the experienced teachers. This Isometric Transformation HOTS test consisted of a pre-and post-test. A pre-test is carried out on a sample before they receive treatment [91]. In this study, a pre-test was conducted before the Form Two students underwent activities for FCLS in the topic of Isometric Transformation. The aim was to detect and determine students' HOTS in completing the Isometric Transformation items before the learning took place. The post-test, on the other hand, is a test conducted on samples receiving treatment to measure the characteristics desired in the experiment [99]. In this study, the post-test was given after the teacher used activities for FCLS or conventional learning strategies for two months. This post-test was conducted with the aim of detecting and determining the student's mastery of HOTS in completing Isometric Transformation items after following activities for FCLS or conventional learning strategies. Both of these tests contained the same content, namely four subjective items that were higher level in solving problems for the Isometric Transformation topic. The Isometric Transformation pre-and post-tests are equivalent sets of tests. According to [100], pretest and post-test questions are supposed to be equivalent, not the same. This is because experimental research that uses the same achievement test can pose a threat to the validity of the study. The fourth stage was the delivery of the instrument to experts for validation.

1) RELIABILITY AND ITEM ISOLATION
In order to determine the reliability of the items in the Isometric Transformation HOTS test, a statistical analysis with the Rasch measurement model was used to obtain the Cronbachalpha reliability value. Based on the analysis, it was found that the Cronbach-alpha reliability value for the construct of applying and analyzing was 1.00. The evaluating construct gave a reliability value of 0.86, while the creating construct gave a reliability value of 0.82. The analysis of the instrument as a whole for the 22 items gave a Cronbach-alpha reliability value equal to 0.81. This shows that all constructs had a high reliability value that was above 0.80, i.e., the constructs were in accordance with the determined sample. According to [101], a Cronbach-alpha value above 0.80 is an acceptable range for research instruments in research.
In the analysis using the Rasch Model, the reliability can also be reported based on the separation of items and respondents, as shown in Table 3.  Table 3 shows the item reliability values for the 22 items in the Isometric Transformation HOTS test. The reliability value of the item (item reliability) was high (0.95). These results clearly prove that the reliability value of the item was effective with a high level of consistency as it approached the value of 1.0. The expected repetition of this item was also high and could be extended to other groups of students. It is most likely that this test could reproduce the hierarchy of the items when the variables were measured [102]. Meanwhile, the item separation value was 4.34 [103], lending evidence that the items could be grouped into four difficulty levels of HOTS.

2) PTMEA CORR VALUE TO DETECT MEASURING CURRENT (POLARITY) ITEM
Next, this study also took into account the polarity value that indicates whether the construct should be measured with the PTMEA CORR value. The PTMEA CORR values of the Isometric Transformation HOTS test are shown in Table 4 (between 0.12 to 0.74). According to [102] if the PTMEA CORR value is positive, the item measures the construct that is supposed to be measured. On the other hand, if the PTMEA CORR value is negative (-), the item does not measure the construct that is supposed to be measured, i.e., the item has to be repaired or dropped. Since the PTMEA CORR value is positive, the 22 items can measure the construct to be measured, move in the same direction as the construct, and do not contradict the construct to be measured.

3) ITEM FIT
Item fit in measuring can be seen through the outfit Mean Square (MNSQ) and infit MNSQ values. Outfit values help detect any outlier or misfit items. Meanwhile, Infit means a match that matches the response pattern to the targeted items and respondents. MNSQ outfit does not cause significant problems in measurement and it is easier to overcome compared to MNSQ infit. Therefore, the researchers checked the MNSQ Outfit to determine the appropriateness of the items that measured a construct. The suggested MNSQ range for polytomous data is 0.5 to 1.5 [102], [104]. Outfit MNSQ values higher than 1.5 are items that are not homogeneous with other items in a measurement scale. Whereas, Outfit MNSQ values that are lower than 0.5 indicate the overlap of constructs with other items. A MNSQ that is out of the MNSQ range will usually show a high z-std value and exceed the accepted range of −2.0 to +2.0. If the MNSQ outfit and infit values are accepted, the Z-std value can be ignored [105].  Based on Table 5, there are 5 items that are identified as being within the unacceptable range, according to the Rasch measurement model, which is item 2(b)(iv) (MNSQ outfit value is 2.09 from the construct analysis). As for the three items from the construct of evaluating, the MNSQ outfit values are as follows: (1) item 3a(ii) = 1.53, (2) item 3b(iii) = 0.37, and (3) item 3b(iv) = 0.37. For the construct of creating, only one item is not in the range, which is item 4(i) (MNSQ outfit value = 0.45). All of these five items are suggested to be refined based on the needs of the researchers and experts' views.

4) UNIDIMENSIONALITY
Further, the researchers used the Rasch model to examine the unidimensional nature of an item being in one direction only [102]. A unidimensional or non-unidimensional construct is examined using a principal component analysis (PCA) [106]. Linacre [107] states that the minimum variance value must exceed 40% to ensure unidimensionality. Table 6 shows the results of the PCA analysis. It can be observed that the PCA value is 47.9%. This result meets the requirements of Linacre [107] and shows that all of these items are multidimensional (items that measure a wide range of dimensions). Meanwhile, the level of the measured item interference or unexplained variance contrast one (unexplained variance 1st contrast) is 10.3%; this value is well controlled and categorized as moderate [108].

VII. RESEARCH FINDINGS
Based on Table 7, the total number of the sample for the control group was 65 consisting of 30 male students (46.2%) and 35 female students (53.8%). Meanwhile, 66 participants consisting of 27 male students (41.0%) and 39 female students (59.0%) were in the treatment group. Each student in the control and treatment groups followed two different learning methods. The students in the control group followed conventional learning methods, while the students in the treatment group received interventions from FCLS activities. The students in the control group who underwent the conventional method learnt the Isometric topic by using textbooks, power point presentations, workbooks and worksheets. The learning activities for the control group took place in the fully physical classroom environment. Meanwhile, the treatment group followed the FCLS activities in which the content of the topic was introduced before the learning took place. The students in the treatment group used the knowledge they gained during the activities in the classroom.

A. ANALYSIS OF NORMALITY
The normality test analysis was carried out in order to determine whether the data collected from the sample was normally distributed or not. There are several ways to conduct the normality test such as Skewness, Kurtosis, Kolmogrov-Smirnov (KS), Anderson-Darling, Cramer-von Mises, Lilliefors statistics and Shapiro-Wilk tests [83]. In the context of this study, the Kolmogorov-Smirnov and Shapiro-Wilk analyses were carried out because the number of samples involved in this study was 131, which was included in the range given, i.e., n>50 for Kolmogorov-Smirnov [109], and 3 ≤ n ≤ 5000 for Shapiro-Wilk [110]. Table 8 shows the analysis based on the Kolmogorov-Smirnov and Shapiro-Wilk normality tests for the control and treatment groups.
Based on Table 8, it can be observed that the significant value of Kolmogorov-Smirnov and Shapiro-Wilk for all Isometric Transformation HOTS pre-and post-tests is 0.00, which is smaller than the value of 0.05. This shows that the data is not normally distributed. Therefore, the appropriate inference analysis used to answer the third research question was the analysis with non-parametric tests. The selection of each analysis for all tests for the control and treatment groups is summarized in Fig. 3 below.
Based on Fig. 3, the Mann-Whitney and Wilcoxon tests were used to answer the research questions of the study.

B. STUDENTS' HOTS IN THE FOUR LEVELS OF THINKING BETWEEN THE TREATMENT GROUP AND THE CONTROL GROUP 1) THE PRE-TEST FOR CONTROL GROUP AND TREATMENT GROUP
The Mann-Whitney test was used to analyze the pre-HOTS test in terms of the four levels of thinking for the control and treatment groups involving 131 samples. This test was performed because the sample consisted of two different VOLUME 11, 2023    groups. Table 9 shows the Mann-Whitney test analysis for the pre-control and pre-treatment groups.
Based on Table 9, the results show that the significant value for the HOTS test across all four HOTS levels is greater than the alpha value of 0.05. This shows that the null hypothesis failed to be rejected. Therefore, it can be concluded that there is no significant difference between the control group and the treatment group for all thinking levels in the pre-HOTS test.

2) PRE-POST TEST FOR CONTROL GROUP AND TREATMENT GROUP
The Wilcoxon test was carried out to analyze the pre-post tests of HOTS for the control group involving 65 samples and the pre-post tests of HOTS for the applying level for the treatment group involving 66 samples. The Wilcoxon test was performed because these data involved samples from the same group. The analysis of the Wilcoxon for the control and treatment groups is shown in Table 10.
Based on Table 10, the results show that the significant value for the HOTS test of the control group's applying, analyzing and creating levels is p=.000, which is smaller than the alpha value of 0.05 (p=.000<.05) but not for the evaluating level.
For the treatment group, a significant result (p=.000) was shown for all thinking levels.

3) THE POST-TEST FOR CONTROL GROUP AND TREATMENT GROUP
The Mann-Whitney test was used to analyze the post-HOTS test for the control and treatment groups involving 131 samples. The Mann-Whitney test was used because these data involved samples from two different groups. The Mann-Whitney test for the post-control and post-treatment groups is shown in Table 11. Based on Table 11, the results show that the significant value for the HOTS test in all thinking levels is p=.000, which is smaller than the alpha value of 0.05 (p=.000<.05). Thus, the null hypothesis is rejected. It can be observed that there is a significant difference between the control group and the treatment group for all thinking levels in the post-HOTS test.

C. STUDENTS' OVERALL HOTS LEVEL BETWEEN THE TREATMENT GROUP AND THE CONTROL GROUP 1) OVERALL PRE-HOTS TEST AND POST-HOTS TEST FOR CONTROL GROUP AND TREATMENT GROUP
The Mann-Whitney test was used to analyze the pre-HOTS test for the topic of Isometric Transformation from the overall achievement for the control group and the treatment group involving 131 samples. This test used samples from two different groups, the control group and the treatment group. Table 12 shows the overall Mann-Whitney test analysis for the pre-control and pre-treatment groups. Based on Table 12, the results show that the significant value for the HOTS Isometric Transformation test in the control group is p=.146, which is greater than the alpha value of 0.05 (p=.146>.05). Therefore, the null hypothesis failed to be rejected. It can be observed that there is no significant difference between the control group and the treatment group in the overall pre-HOTS test. The results show a significant value for the Isometric Transformation HOTS test for the treatment group (p=.000), which is smaller than the alpha value of 0.05 (p=.000<.05). Thus, the null hypothesis is rejected. It can be seen that there is a significant difference between the control group and the treatment group for the overall post-test HOTS.

A. THE APPLYING LEVEL IN THE TOPIC OF ISOMETRIC TRANSFORMATION
The findings of the study show that the implementation of FCLS can improve the applying level in the topic of Isometric Transformation. The improvement of students' HOTS from the aspect of the applying in the topic of Isometric Transformation not only has a positive impact but also accords well with the claim in [45] in which the authors state that students are more successful in solving Isometric Transformation problems in new situations. This happens because FCLS contains various activities during learning sessions either outside or inside the classroom which can have a positive impact on the students' mastery of HOTS from the applying level for the topic of Isometric Transformation. This is supported through the game methods during learning periods outside the classroom in FCLS.
The game methods related to daily life are given during learning sessions outside the classroom. For example, students play DAM digitally or non-digitally and are required to take pictures and upload them in Google Classroom or WhatsApp. This game method has indirectly helped students understand translation concepts related to their daily life. This is in line with the claim in [111] in which the authors state that the use of game elements in the learning process can motivate students to complete challenging exercises, unlike those students who are not involved in game elements. Moreover, [76] also state that the element of games in flipped classrooms improves problem-solving skills in learning mathematics. Therefore, the results of this study show that there is a significant improvement in the students' HOTS from the applying level for the topic of Isometric Transformation. This proves that FCLS is indeed able to help improve students' HOTS from the aspect of the applying level for the topic of Isometric Transformation.

B. THE ANALYZING LEVEL IN THE TOPIC OF ISOMETRIC TRANSFORMATION
The findings of the study prove that the implementation of FCLS can improve the analyzing level in the topic of Isometric Transformation. The increase in HOTS in the treatment group shows that the implementation of FCLS provides a way for students to use analytical skills in assignments to categorize, differentiate, compare, and solve problems in the topic of Isometric Transformation with the help of peers. This is supported through the implementation of group activities during learning periods in the classroom. In this way, students can interact with group members and learn with more skilled friends to avoid misconceptions in the topic. This indirectly shows that students try to avoid misconceptions and promote the improvement of students' mastery of HOTS in the topic of Isometric Transformation [78].
The findings of this study are in line with the findings by [112] which states that with the help of peers, students can solve mathematics problems accurately. Moreover, [113], on the other hand, claim that the method of obtaining the answer to mathematics questions by peers is different from the way the teachers present it. This finding also coincides with the study by [114] who states that, through discussions in small groups, students can understand a concept in greater depth and can explain it to other friends.
As explained in the Social Constructivism Theory which emphasizes teacher guidance, peers in the implementation of FCLS can play a role in helping students understand mathematics concepts. This is particularly critical when students learn outside the classroom in which they can use the Internet to answer the quizzes given. If students are not confident with the answers obtained, they can discuss with their peers, teachers or refer to the Internet. This finding is supported in [115] in which the authors prioritize the Social Constructivism theory in the implementation of flipped classrooms and peer guidance that help develop students' potential in learning mathematics.
The authors in [116] also support the findings of the current study by asserting that learning outside the classroom creates the value of cooperation and mutual help between peers and teachers. Collaborative learning between excellent, average and weak students in a group can improve students' understanding [117]. The value of this collaboration can encourage students to think positively about mathematics and motivate them to learn mathematics in a better way [118].

C. THE EVALUATING LEVEL IN THE TOPIC OF ISOMETRIC TRANSFORMATION
The findings of the current study show that the implementation of FCLS can improve the evaluating level in the topic of Isometric Transformation. The increase of HOTS in the treatment group proves that the implementation of FCLS provides space for students to make generalizations about transformation patterns by using different learning strategies linked to their daily life in the topic of Isometric Transformation. This is consistent with the claim reported in [44] in which the authors support communication skills in learning outside or inside the classroom. This method helps other groups to evaluate ideas or information related to the topic of Isometric Transformation. This is further supported through the project method implemented outside the classroom in FCLS.The project method for the rotation sub-topic is given in the form of a video to the students. They are required to use recycled items to make a project and upload them in Google Classroom or WhatsApp. This project method has indirectly helped students understand the concept of rotation related to their daily life. Likewise, the same finding was found in [65], i.e, project-based learning in FCLS helps students apply mathematical concepts in their daily life. The findings of this study prove that the implementation of FCLS can have a positive impact [115] on students' mastery of HOTS from the aspect of the evaluating level for the topic of Isometric Transformation. This process is implemented through watching videos and answering quiz questions for the concept of rotation before class to help students make connections to the topics. Then, this process is followed by the second phase of applying and strengthening the concept through the continuation of learning outside the classroom. Students, then, answer the applying and analyzing questions followed by the evaluating questions through group discussions. Communicating with group members is in line with the claim laid out in [71] in which the author asserts that group presentations allow students to exchange opinions on new knowledge and ultimately build their thinking skills, knowledge and assessment skills [74].
This finding proves that FCLS can stimulate students' assessment skills. In this way, students can communicate with group members and learn with friends who are more skilled to answer questions in the assessment aspect [57]. Therefore, project-based learning before class in FCLS helps students answer HOTS questions easily. In the current study, the students who went through this intervention explained that the various activities related to their daily life brought about cognitive changes and increased their HOTS mastery.
The findings of this study are also in line with the claim in [119] in which the author states that FCLS in learning mathematics contributes to the cognitive development of students without time constraints. This FCLS is student-centered and provides maximum opportunities for students to use their time to understand mathematics concepts [120]. Moreover, [121] and [122] also agree that FCLS helps students improve their understanding in learning mathematics. Likewise, [123] explain that teaching aids make students more confident in learning mathematics, especially in the topic of Isometric Transformation.
Furthermore, [124] emphasize that creative teaching aids and visual tools can stimulate students' creative thinking. The findings of the current study support previous studies that show a positive relationship between teaching aids and student's mastery of HOTS [125]. The finding also shows that FCLS can improve the mastery of students' HOTS from the aspect of the evaluating level for the topic of Isometric Transformation. This clearly proves that FCLS is more successful in influencing students' HOTS mastery from the aspect of the evaluating level for the Isometric Transformation topic compared to the control group who applies conventional learning strategies.

D. THE CREATING LEVEL IN THE TOPIC OF ISOMETRIC TRANSFORMATION
The findings of the study show that the implementation of FCLS can improve the creating level in the topic of Isometric Transformation. The increase of HOTS in the treatment group proves that the implementation of FCLS provides space for students to use their cognitive skills to connect ideas and build new forms in the answer space. This is supported through communication skills in learning outside and inside the classroom. This environment demands students to present answers to other groups so that they can evaluate ideas or information related to the topic of Isometric Transformation.
The findings of this study also show that the implementation of FCLS can have a positive impact on the mastery of students' HOTS from the aspect of the creating level for the topic of Isometric Transformation [126]. For example, the sub-topics of Translation, Reflection and Rotation as Isometry are introduced to learning outside the classroom by providing videos related to daily life [127]. Next, the learning process is followed by quiz questions for the concept of Translation, Reflection and Rotation as Isometry before the class starts in order to test the level of students' understanding. This will make teachers more prepared and face various questions from students more effectively. Then, this process is followed by the second phase of applying and strengthening the concept through the continuation of learning outside the classroom. Students complete a comprehensive exercise that focuses on applying, analyzing, and evaluating. This is followed by creating questions through group discussions until they successfully create a form and provide justifications. This finding also proves that FCLS can stimulate students' creative skills [128]. Collaborative efforts among students and teachers through 21st century learning can help students answer creative questions. Therefore, collaborative learning that exists in FCLS can help students answer HOTS questions easily. This finding is in line with [129] who states that continuous learning and collaborative skills in group activities can help improve students' mastery of HOTS. Likewise, [130] asserts that FCLS is critical in the development and implementation of learning activities.

E. STUDENTS' OVERALL HOTS IN THE TOPIC OF ISOMETRIC TRANSFORMATION
The findings of the current study show that the implementation of FCLS can significantly increase the students' mastery of HOTS as a whole in the topic of Isometric Transformation. The increase of HOTS in the treatment group proves that the implementation of FCLS gives space for students to use VOLUME 11, 2023 their cognitive skills. This is supported through collaborative efforts in learning outside and inside the classroom. FCLS is a strategy that prioritizes HOTS inside and outside the classroom [89], [127]. HOTS is necessary for each student at every level of education and in every subject [131]. Mathematics also prioritizes HOTS. The implementation of HOTS in learning mathematics aims to change students' perception and increase their interest in learning mathematics [132]. Therefore, the researchers used FCLS as a strategy to develop HOTS inside and outside the classroom.
As suggested by [68], teachers need to focus on the implementation of FCLS, especially before learning begins. Moreover, [133] explain in detail the implementation of FCLS through videos. In their study, videos are used to explain each sub-topic, such as translation, reflection and rotation, in the context of students' daily life. This in turn helps students relate their knowledge and skills in obtaining mathematical information [37]. For example, the sub-topic of Rotational Symmetry is introduced by providing videos related to students' daily life. Next, this activity is followed by a quiz for the concept of Rotational Symmetry before the class starts so that it will be easier for students to apply their knowledge. Moreover, [134] also support the method of giving quizzes in FCLS so that students are given opportunities to improve their problem-solving skills.
Then, this process is followed by the second phase of applying and strengthening the concept through the continuation of learning outside the classroom. Students answer the applying, analyzing, evaluating, and creating questions through group discussions until they successfully create the given tiles. Comprehensive training that focuses on HOTS has clearly proven to help students improve their mastery of HOTS.
The statement above clearly shows that students are more likely to use FCLS in their learning strategies. Specifically, this FCLS helps students understand the Isometric Transformation topic in greater depth [135]. FCLS can enhance the relationship between teachers and students when students need guidance. Students can get help from teachers or more skilled people through social media [136] without time constraints. Furthermore, [137] assert that FCLS provides more time for active learning and problem-solving activities. Likewise, [138] states that FCLS can increase creativity and stimulate knowledge to solve HOTS problems.

IX. CONCLUSION
The current study provides meaningful theoretical and practical implications. The development of the Flipped Classroom Learning Strategy (FCLS) for the improvement of HOTS in the Isometric Transformation topic can be used as a guide to manage mathematics learning more effectively. The implications of this study can be divided into two parts, which are theoretical implications and practical implications. FCLS has integrated the Theory of Social Constructivism in the learning of mathematics, especially for the topic of Isometric Transformation. Based on the findings of the study, the use of FCLS has succeeded in significantly increasing students' mastery of HOTS. FCLS prioritizes student-centered learning and does not encourage conventional learning to deepen the topic of Isometric Transformation. This is so because every learning activity prioritizes integration with other people with more skills based on the principle of the Zone of Proximal Development (ZPD). This is achieved through watching videos, accessing additional notes, and group discussions. The three phases in FCLS emphasize student-centered learning activities to increase students' understanding in the topic of Isometric Transformation and provide opportunities for students to interact socially with their teachers and peers. FCLS has given implications in general to teachers' pedagogical practices that focus on the construction of students' mathematics HOTS knowledge in the topic of Isometric Transformation. FCLS is equipped with a lesson plan and a guide in conducting various methods. Comprehensive training on HOTS will make it easier for teachers to integrate HOTS in their classroom. FCLS helps teachers to attract students' attention, interest and confidence in the topic of Isometric Transformation. Nevertheless, the effectiveness of FCLS depends on the expertise of teachers in choosing appropriate skills. Teaching resources not only increase students' mastery of HOTS in the topic of Isometric Transformation, but also produce quality mathematics teachers. This indirectly supports 21st century pedagogic practices that promote ICT skills and diversity in knowledge delivery techniques, which are in line with MOE's objectives MOHD HILMI HAMZAH received the Ph.D. degree in phonetics from the University of Melbourne, Australia. He is currently an Associate Professor with the School of Languages, Civilisation and Philosophy, Universiti Utara Malaysia (UUM), Kedah, Malaysia. His research interests include phonetics and phonology, applied linguistics, and speech science and technology.