In a two-sample t-test, the grouping variable should be which type?

In a two-sample t-test, the grouping variable should be which type?

• A. Categorical with only two categories (dichotomous)
• B. Continuous
• C. Categorical with three or more categories
• D. Ordinal

Answer: (A)

The test compares the average outcome between two separate groups, so the grouping variable must define exactly two categories. A binary, dichotomous categorical variable creates two independent samples whose means you can contrast. If the grouping variable has more than two categories, you’d need a method that handles multiple groups, like ANOVA, to compare all means. If the grouping variable were continuous, you wouldn’t form two groups to compare; instead you’d analyze the relationship between the continuous factor and the outcome via regression or correlation. So the standard setup uses a categorical variable with two categories, such as treatment vs. control, to split the data into two groups for comparing their means.

The test compares the average outcome between two separate groups, so the grouping variable must define exactly two categories. A binary, dichotomous categorical variable creates two independent samples whose means you can contrast. If the grouping variable has more than two categories, you’d need a method that handles multiple groups, like ANOVA, to compare all means. If the grouping variable were continuous, you wouldn’t form two groups to compare; instead you’d analyze the relationship between the continuous factor and the outcome via regression or correlation. So the standard setup uses a categorical variable with two categories, such as treatment vs. control, to split the data into two groups for comparing their means.