What are the important factors affecting prognostics?

Trend analysis mathematics and data interactions are studied. Investigation of the tolerances on the projection of the linear trend line is undertaken. Importance of the number of measurements is discussed. It is shown that the best estimate of time to exceedance requires 8 to 9 measurements. Several examples of test data are presented. The relationship between requirements and test equipment performance is given. Two different methods to determine accuracy of prediction are discussed. Some methods of trend analysis have only limited ability and experience with accuracy of prediction questions. Based on experience with vehicle testing the major limitation has been non-repeatability of data.