The Wilcoxon Signed Rank Test Critical Values Table is a key tool for interpreting the results of the Wilcoxon Signed Rank Test, a non-parametric statistical test used to compare two related samples. Here’s a breakdown of the table and its explanation:
What it contains:
- Sample size (n): This refers to the number of paired observations in your data.
- Significance level (α): This represents the probability of rejecting the null hypothesis (H0) when it’s actually true, typically set at 0.05 (5%) or 0.01 (1%).
- Critical values: These are specific thresholds for your Wilcoxon signed-rank statistic (W) based on n and α.
How to use it:
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Calculate your Wilcoxon signed-rank statistic (W): This involves ranking the absolute differences between paired observations, considering their signs, and summing the positive ranks.
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Look up the critical value based on your sample size (n) and chosen significance level (α): Each combination of n and α has a corresponding critical value in the table.
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Compare your calculated W to the critical value:
- Two-tailed test: If your W is less than or equal to the critical value, reject the null hypothesis (H0) and conclude that there is a significant difference between the paired samples.
- One-tailed test: Double your chosen α and use the table accordingly. Reject H0 if W is less than or equal to the adjusted critical value for the desired direction of change (e.g., only positive differences).
