Wilcoxon Signed Ranks Test

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Non-parametric alternative for One Sample t-Test and Repeated Measures t-Test

Repeated measures study;

one individual measured twice

the difference between two measurements is recorded as the "SCORE" for that individual

Used to evaluate the difference between two measurements using the data from a repeated measures experiment

Test REQUIRES that the differences be rank ordered from smallest to largest in terms of magnitude without regard for sign or direction

LOGIC of the Wilcoxon test -

uses the signs and the ranks of different scores to decide whether there is a significany difference between the treatments or not

NULL HYPOTHESIS: no consistent, systematic difference (if hypothesis is true it is due to chance)

ALTERNATIVE HYPOTHESIS: scores show a consistent difference

after computing differences and calculating test statistic, the smaller of the sums is the test statistic

null hypothesis is rejected if the test statistic is less than or equal to the critical value