Incremental Sampling Process for Actual Function Points Validation in a Contract, An Empirical Experiment

Customer verification of functional size measures provided by the supplier in the acceptance phase is a critical task for the correctness of contract execution. A lack of control by the customer, both in depth and in scope, can lead to relevant deviations of the actual unitary price if compared to that accepted in the bid assignment process, with potential consequences in terms of unfairness or, in some cases, illegality. In this paper we summarize an efficient and well defined approach to validate supplier's functional size measurements in order to present the validation experiment. This approach was extensively presented at SMEF 2012. The approach, although statistically based, is rigorous, since it defines clear and unambiguous game roles, and efficient, in order to spend the adequate effort to achieve the expected confidence about supplier's functional size measurement capabilities. The approach consists in applying a variation of the Incremental Sampling Method that allows the customer tuning the validation effort on the quality level of size measures provided by the supplier, detected by the gap among these measures and the ones checked and validated on a sampled base. An empirical validation experiment, which is the focus of the present paper, is presented to illustrate the advantages of the approach.