Which situation represents a threat to internal validity in an experimental study measuring the effect of a videotape of home-going instructions for patients being discharged after coronary artery bypass graft surgery?
A) Both men and women were included as subjects in the study.
B) Two new surgeons began performing the coronary artery bypass graft surgeries.
C) Patients in the experimental group discussed aspects of the tapes with patients in the control group.
D) Data collection took 1 year.

Question

Quizplus · Accepted Answer

Correct C: Sharing aspects of the tapes with control group members interferes with interpretation of the true effect of the independent variable.
Incorrect A: Including both genders would be a design strength,not a threat to internal validity.
Incorrect B: Personnel factors like surgeons' newness should not directly affect the treatment and threaten internal validity.
Incorrect D: Duration of data collection does not threaten internal validity,provided that control processes were standardized.

Which Situation Represents a Threat to Internal Validity in an Experimental