has part is about has_specified_input has_specified_output achieves_planned_objective is denoted by data set population statistical hypothesis test objective study design independent variable study design dependent variable data transformation false positive rate Mann-Whitney U-test 1 1 2 1 Wilcoxon rank-sum test U test Orlaith Burke Alejandra Gonzalez-Beltran Philippe Rocca-Serra The Mann-Whitney U-test is a null hypothesis statistical testing procedure which allows two groups (or conditions or treatments) to be compared without making the assumption that values are normally distributed. The Mann-Whitney test is the non-parametric equivalent of the t-test for independent samples Wilcoxon Rank-Sum test adapted from http://udel.edu/~mcdonald/statkruskalwallis.html and from http://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U last accessed [2014-03-04] rank-sum test for the comparison of two samples scipy.stats.mannwhitneyu(x, y, use_continuity=True) http://docs.scipy.org/doc/scipy/reference/generated/scipy.stats.mannwhitneyu.html#scipy.stats.mannwhitneyu source: https://github.com/scipy/scipy/blob/v0.15.1/scipy/stats/stats.py#L4049 scipy.stats.ranksums(x, y) http://docs.scipy.org/doc/scipy/reference/generated/scipy.stats.ranksums.html#scipy.stats.ranksums source: https://github.com/scipy/scipy/blob/v0.15.1/scipy/stats/stats.py#L4103 wilcox.test(dependent variable ~ independant variable, data = dataset) http://stat.ethz.ch/R-manual/R-patched/library/stats/html/wilcox.test.html dichotomous variable ranking non-parametric test probability distribution normal distribution continuous variable between group comparison objective p-value ready for release