What term describes the variables that are deliberately manipulated in an experiment?

• A. Factors
• B. Levels
• C. Dependent variables
• D. Covariates

Answer: (A)

In experimental design, the thing you deliberately change to see its effect is a factor. A factor is any variable whose impact you want to study by manipulating its value or condition. Each factor can have multiple levels, which are the specific settings you test (for example, different doses or conditions within that factor). The outcome you measure to assess the effect is the dependent variable. Covariates are other variables you account for because they might influence the outcome, but you don’t manipulate them to test a cause-and-effect relationship.

So, the manipulation you control in an experiment is best described as a factor. The other terms fit different roles: levels are the specific values of a factor, the dependent variable is what you measure, and covariates are extra variables you control for or include in analysis.