Which situation represents a threat to internal validity in an experimental study measuring the effect of a videotape of discharge instructions for patients who underwent coronary artery bypass graft (CABG)surgery?

Question

Quizplus · Accepted Answer

Patients in the experimental group discussing aspects of the videotape with patients in the control group can contaminate the results and affect internal validity by allowing the control group to receive some of the treatment. This is known as diffusion of treatment. A key aspect of experimental design is keeping the experimental and control groups separate to minimize the influence of extraneous variables. The other options do not directly affect the internal validity of the study.

Which Situation Represents a Threat to Internal Validity in an Experimental