A program is evaluated during a period of a major external event that could influence outcomes. This creates vulnerability to which threat to internal validity?

A program is evaluated during a period of a major external event that could influence outcomes. This creates vulnerability to which threat to internal validity?

• A. History
• B. Maturation
• C. Selection bias
• D. Instrumentation

Answer: (A)

When a study takes place during a period dominated by a major external event, outcomes can change because of that event rather than because of the program being evaluated. This is known as a history threat to internal validity. The key idea is that something happening outside the study setting—like a policy shift, economic crisis, or natural disaster—can influence participants' results across the board, making it hard to tell whether observed changes are due to the program or the event. This differs from maturation, which are natural changes that occur over time within participants; from selection bias, which arises when groups aren’t comparable at the start; and from instrumentation, which involves changes in measurement tools or procedures. In the scenario described, the critical factor is the external event occurring during the evaluation period, which can confound the program’s true effect. Mitigation strategies include using a concurrent control group or employing designs that track outcomes across multiple time points to separate the program impact from the event’s influence.

When a study takes place during a period dominated by a major external event, outcomes can change because of that event rather than because of the program being evaluated. This is known as a history threat to internal validity. The key idea is that something happening outside the study setting—like a policy shift, economic crisis, or natural disaster—can influence participants' results across the board, making it hard to tell whether observed changes are due to the program or the event.

This differs from maturation, which are natural changes that occur over time within participants; from selection bias, which arises when groups aren’t comparable at the start; and from instrumentation, which involves changes in measurement tools or procedures. In the scenario described, the critical factor is the external event occurring during the evaluation period, which can confound the program’s true effect. Mitigation strategies include using a concurrent control group or employing designs that track outcomes across multiple time points to separate the program impact from the event’s influence.