Nonparametric statistical tests

Nonparametric statistical tests are used instead of the parametric tests we have considered thus far (e.g. t-test; F-test), when:

The following are some common nonparametric tests:

Chi square: c2

1. used to analyze nominal data

2. compares observed frequencies to frequencies that would be expected under the null hypothesis

Mann-Whitney U

1. compares two independent groups on a DV measure with rank-ordered (ordinal) data

2. nonparametric equivalent to a t-test

Wilcoxon matched-pairs test

1. used to compare two correlated groups on a DV measured with rank-ordered (ordinal) data

2. nonparametric equivalent to a t-test for correlated samples

Kruskal-Wallis test

1. used to compare two or more independent groups on a DV.with rank-ordered (ordinal) data

2. nonparametric alternative to one-way ANOVA