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Choosing a non-parametric test

Explanations > Social Research > Analysis > Choosing a non-parametric test

Choosing the test

Use the table below to choose the test. See below for further details.

How many separate samples?

How many scores for each subject?

How many measurement categories?
2	Binomial test
2+	Chi-square test for goodness of fit

Can difference scores be ranked?
Y	Wilcoxon test
N	Sign test

Matched samples? (N = independent)

Can difference scores be ranked?
Y	Wilcoxon test
N	Sign test

Can scores be ranked with few tied values? (independent samples only)
Y	Median test
Y	Mann-Whitney test
N	Chi-square test for independence

Can scores be ranked with few tied values? (independent samples only)
Y	Median test
N	Chi-square test for independence
N	Krushkal-Wallas test

Non-parametric tests do not assume an underlying Normal (bell-shaped) distribution.

There are two general situations when non-parametric tests are used: