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Which test?

Table 1. Some common tests for simple comparisons and when they should be used.


Characteristics of outcome variables


Continuous, normal

Continuous, non-normal OR discrete


Compare one mean with a population value/ Describe one mean

One sample z-test/ t-test

 One sample z-test if the   sample size is large

One sample z-test/ exact binomial test

Compare 2 independent groups

Independent samples z-test/ t-test

Mann-Whitney U/ Wilcoxon Sum of ranks

Chi-squared test or Normal approximation or Fisher’s exact test

Compare 2 paired/ matched groups

Paired t-test

Wilcoxon signed ranks test/ sign test

McNemar’s test

Compare 3 or more independent groups

One way Analysis of Variance

Kruskal Wallis test

Chi-squared test or ordinal chi-squared test

Compare 3 or more matched groups

Repeated measures Analysis of variance

Friedman test

Cochrane Q