When should rank regression or maximum likelihood estimation (MLE) be used when conducting life data analysis in Weibull++?
When analyzing life data in Weibull++, you need to select a method for estimating the parameters for your chosen distribution: rank regression on X (RRX) or Y (RRY) or maximum likelihood estimation (MLE). How do you know which method is most appropriate? Regression generally works best for data sets with smaller sample sizes (as sample sizes get larger, 30 or more, these differences become less important) that contain only complete data (i.e. data in which all of the units under consideration have been run or tested to failure). There are two forms of regression: regression on X and regression on Y. Failure-only data is best analyzed with rank regression on X, as it is preferable to regress in the direction of uncertainty. If a reliability test is repeated with the same number of units operated to failure in each experiment, the failure times would change from test to test, but the rank values would remain the same, since they are based solely on sample size and order number. Hence, th
