What is an implication of having a control group in a study?

Having a control group in a study primarily contributes to increased potential for internal validity. Internal validity refers to the degree to which a study accurately establishes a cause-and-effect relationship between the independent variable (the variable being manipulated) and the dependent variable (the outcome being measured). By including a control group, researchers can compare the effects of the treatment or intervention against a group that does not receive the treatment, thus isolating the effects of the independent variable.

This comparison is crucial for ruling out alternative explanations for the observed results, such as confounding variables or biases that might affect the outcome. A control group helps to ensure that any changes in the dependent variable can be more confidently attributed to the treatment being studied, rather than other external factors.

The other options do not accurately reflect the primary implications of having a control group. For instance, while a control group might influence the sample size needed, it doesn’t inherently decrease it; rather, it often requires more participants to achieve adequate power. The presence of a control group does not necessarily reduce the time for data collection, and it typically has the opposite effect on external variability, as the control group can help clarify the specific results relating to the treatment.