Refer to given Exercise, describing a case-control study relating childhood diet and heart disease. Comment on the extent to which each of the following is likely to be a problem.

a. Confounding variables and the implication of causation in observational studies.

b. Extending results inappropriately.

c. Interacting variables.

d. Hawthorne and experimenter effects.

e. Ecological validity and generalizability.

f. Relying on memory or secondhand sources.

Exercise
Pick the two "difficulties and disasters" that are most likely to be a problem in the following study, and explain why each would be a problem: A researcher at a large medical clinic wants to determine whether a high-fat diet in childhood is more likely to result in heart disease in later life. As a case- control study, she gives a questionnaire about childhood diet to 500 patients with heart disease and 500 patients without heart disease matched by age and sex.