Which of the following is an example of a fixed variable?

• A. Gender
• B. Age
• C. Time
• D. Temperature

Answer: (A)

A fixed variable is a factor whose categories are predetermined by the researcher and are the specific levels you want to compare. The idea is you’re interested only in those particular categories, not in generalizing to other possible categories.

Gender fits this description because it’s a categorical attribute with a small, fixed set of categories (for example, male and female) that the analysis compares directly. The levels are defined by the study and are the focus of the comparison.

Age, time, and temperature are typically treated as variables that can take many values or be measured across conditions, often used as covariates or continuous predictors rather than fixed factors. They can vary widely and aren’t usually the specific, limited categories of interest that define a fixed factor.