Should I use a dependent samples t-test or repeated measures ANOVA?

Quantitative Results
Statistical Analysis

For students learning about statistics, some ask whether they should use an dependent samples t-test (also called a paired samples t-test) or a repeated-measures ANOVA.  Let’s start at the beginning.  Both of these tests assess differences across the same observations (or pairs) on scale level variables.  For example, is there a difference in GPA at time 1 and GPA at time 2, or is there partner agreement on Extraversion, etc.

Assumptions

Both the dependent samples t-test and the repeated measures ANOVA have the same assumptions: normality and homogeneity of variance.  You can assess the normality assumptions with a Shapiro-Wilk test or a Q-Q scatterplot. You can assess the homogeneity of variance with Levene’s test. A non-significant result in the Shapiro and Levene tests indicates that the paired sample t-test or repeated measures ANOVA assumptions are met.

So which one should I use?

For a test at two time points or with paired samples, the t-value and F-value are equivalent. If the probability is ≤ 0.05, the means differ.

Caveat

Use repeated measures ANOVA for three or more time points or values. The t-test only works with two.

Try www.IntellectusStatistics.com free for a week, download a dataset, and run both tests.

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