Assumptions #1 and #2 are explained below: If these assumptions are not met, there is likely to be a different statistical test that you can use instead. However, you should check whether your study meets these two assumptions before moving on. You cannot test the first two of these assumptions with Minitab because they relate to your study design and choice of variables. The Wilcoxon signed-rank test has three "assumptions". However, before we introduce you to this procedure, you need to understand the different assumptions that your data must meet in order for a Wilcoxon signed-rank test to give you a valid result.
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In this guide, we show you how to carry out a Wilcoxon signed-rank test using Minitab, as well as interpret and report the results from this test. Alternately, you could use a Wilcoxon signed-rank test to understand whether there is a difference in productivity based on whether packers in a factory listen to background music (i.e., the dependent variable would be "productivity", measured in terms of the number of parcels packers processed per day, and the two related groups would be the two different "conditions" participants were exposed to that is, the number of parcels processed when packers listen to background music (condition A) compared to the number of parcels processed when packers do not listen to background music (condition B)). As the Wilcoxon signed-ranks test does not assume normality of the differences of the two related groups, it can be used when this assumption has been violated and the use of the paired t-test is inappropriate.įor example, you could use a Wilcoxon signed-rank test to determine whether there is a difference in the number of customer complaints before and after a training course for sales reps designed to improve their customer interactions (i.e., the dependent variable would be “customer complaints”, and the two related groups would be the two different “time points” that is, the number of customer complaints “before” the training course and the number of customer complaints “after“ the training course. It is the nonparametric equivalent to the paired t-test. The Wilcoxon signed-rank test determines whether there is a statistically significant difference in the median of a dependent variable between two related groups. Wilcoxon signed-rank test using Minitab Introduction
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