Question

A researcher wants to investigate a connection between systolic blood pressure and body type to see if those with different body types had different systolic blood pressures on average. Body type is a categorical variable with levels 0 = Normal, 1 = Overweight, and 2 = Obese.

Why should the researcher not use two-sample t-tests to see what the differences are between the means of these three groups?

Answer 1

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When more than 2 groups are compared, some researchers erroneously apply the t test by implementing multiple t tests on multiple pairs of means. It is inappropriate because the repetition of the multiple tests may repeatedly add multiple chances of error, which may result in a larger α error level than the pre-set α level. Hence, ANOVA must be used instead of multiple t-tests so that error is taken care of.