The nurse is conducting a study on how regular physical activity affects the risk for developing lung cancer among smokers. One group leads a sedentary lifestyle whereas the other has agreed to undergo regular supervised exercise in the gym of a local hospital. During the study, the sole treadmill in the gym broke down and was unable to be used for the last half of the study. Several study participants who preferred the treadmill to other machines did not exercise as long or as intensely as they might otherwise have. Which threat to the external validity of the study does this represent?

Question

Quizplus · Accepted Answer

The breakdown of the treadmill represents an "Interaction of history and intervention" threat to external validity. This is because an external event (the treadmill breaking down) interacted with the intervention (regular supervised exercise), potentially affecting the study's outcomes and its generalizability to other settings or populations.

The Nurse Is Conducting a Study on How Regular Physical