Which term refers to the cause or influence on the dependent variable?

• A. Dependent Variable
• B. Confounding Variable
• C. Independent Variable
• D. Outcome Measure

Answer: (C)

The cause or influence on what you measure is the independent variable. In study design, you identify the dependent variable as the outcome you observe or measure, and you then consider what factor you intentionally change to see if it produces a difference in that outcome. The independent variable is the presumed driver of any observed change in the dependent variable.

For example, in an infection-control study, you might vary whether a new hand hygiene protocol is used. The protocol itself is the independent variable, because you’re testing its effect. The rate of infections is the dependent variable, because that rate is what you measure to see if it changes in response to the protocol. It’s also important to be aware of confounding variables—other factors that can influence the dependent variable and may be related to the independent variable—which is why controlling or randomizing helps isolate the true effect. The outcome measure refers to the specific metric used to quantify the result (often the same as the dependent variable, such as infections per 1,000 patient-days).