What best defines 'variable' as used in the biomedical research field?

• A. It refers to something that cannot be measured accurately
• B. It represents anything that is not controlled during the study
• C. It refers to what is being measured during the study
• D. It represents anything that can affect the results of a study

Answer: (D)

In biomedical research, a variable is any factor that can influence the study’s results. This can be a biological trait like age or sex, an environmental condition such as temperature or housing, or a procedural factor like dose timing or sample handling. Because these factors can change outcomes, they must be considered when planning experiments and interpreting data.

Variables can be things you purposely change (independent variables) to see their effect, or things you measure to determine the response (dependent variables). Many studies also include variables you keep constant to reduce unintended influences, or acknowledge as potential confounders if they’re not controlled.

For example, in a drug study with mice, the dose is the independent variable, the measured response (like a biomarker) is the dependent variable, and factors like age, sex, and housing are variables you try to control to prevent them from biasing the results. This broad idea—any factor that could affect results—is why a variable is defined as such.