Rank function in TI Nspire for Wilcoxon signed rank test

The Wilcoxon signed rank test is a non-parametric method for t-test under situation where normal distribution cannot be assumed on the sample data.

There is no built-in function for this hypothesis test in the TI Nspire, but the process is straight forward. During the calculation of the W statistic, a ranking process is required on the sorted input list. For ties, the handling is to assign the average value of the span of the tie. It is easy to create the ranking list using the built-in newlist() function, but for assigning this particular ranking rule, a program is created to facilitate.

The core part of this program is to iterate through an input list (assumed sorted with the SortA function), and the check if there is duplicates using the countIf() function.

The sample usage in calculator is easy.

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