Which statistical test is used when comparing three or more groups?

• A. Chi-square test
• B. Analysis of Variance
• C. Student's t-test
• D. Mann-Whitney U Test

Answer: (B)

When you have three or more groups and want to know if their average values differ, you use analysis of variance. ANOVA compares how much of the total variation is due to differences between group means versus variation within each group. If the test shows a significant result, it means at least one group mean is different from the others, and you follow up with post hoc tests to pinpoint which groups differ. This method assumes that observations are independent, the data are approximately normally distributed within each group, and variances are similar across groups. If those assumptions aren’t met, a nonparametric alternative like Kruskal-Wallis can be used, which compares group ranks rather than means. Other options aren’t appropriate here: the chi-square test handles categorical data, not means; a t-test compares only two groups at a time (and doing multiple t-tests inflates error); and the Mann-Whitney U test is the nonparametric counterpart to a two-group t-test, not suited for three or more groups.