What is the Wilcoxon matched pair sign test?
The Wilcoxon matched pair sign test is a non-parametric hypothesis test that is used to compare the medians of two dependent samples.
For example, let’s say there are 10 rabbits. A certain treatment is provided to the rabbits. And the weights of the rabbits before and after the treatment are recorded.
Now, we want to know whether the difference in the medians of the weights of the rabbits before and after the treatment is statistically significant.
The Wilcoxon matched pair sign test is the non-parametric alternative of the paired t-test. We perform the Wilcoxon matched pair sign test when the data is not distributed normally.
How is the Wilcoxon matched pair sign test performed?
Let’s say we are given the weights of 10 rabbits before and after a certain treatment. And we want to know whether the difference between the medians of the rabbits before and after treatment is statistically significant. To do so, we need to perform the following steps:
1. We will first find out the difference between two weights for each rabbit before and after the treatment.
2. Then, we will rank the absolute differences in ascending order.
3. If the difference associated with two or more ranks is the same, we will replace the ranks with the average rank. For example, if the difference associated with ranks 2, 3, and 4 are the same, we will replace ranks 2, 3, and 4 with the average of 2, 3, and 4, which is 3.
4. We will then assign a sign with each rank. If the difference associated with a rank is positive, we will assign a positive sign. And if the difference associated with a rank is negative, we will assign a negative sign.
5. We will now calculate W+ and W-. W+ is the sum of positive ranks, and W- is the sum of negative …






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