What is the primary purpose of a t-test?

• A. Parametric measure to compare two sample means
• B. Nonparametric test used to compare two variances
• C. Measure of association between two variables
• D. Test of normality for a single sample

Answer: (A)

The main idea of a t-test is to determine whether the average values of two groups are different in a way that is unlikely to occur by chance. It’s a parametric method, meaning it relies on assumptions about the data distribution (roughly normal) and, in the common version, about equal variances between groups. The test produces a t-statistic and a p-value that tell you whether the observed difference in means is statistically significant. This is exactly what you’d use when asking questions like whether a new treatment changes the average outcome compared to a standard treatment. It isn’t about variances, nor about measuring a relationship between two variables, nor is it a normality test for a single sample.