Which Situation Represents a Threat to Internal Validity in an Experimental

question 5

Multiple Choice

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.

---

Definitions:

Lymphocytes

A type of white blood cell that is part of the immune system, involved in protecting the body against both infectious disease and foreign invaders.

Phagocytes

Cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells.

Venous Circulation

Venous circulation refers to the system of veins and venules that return deoxygenated blood from the body back to the heart.

Cisterna Chyli

A dilated sac at the lower end of the thoracic duct into which lymph from the intestinal trunk and two lumbar lymphatic trunks flow.