Depression, revisited. Consider again the study of the association between depression and cardiac disease survivability in Exercise 18.

a) Create a 95% confidence interval for the difference in survival rates.

b) Interpret your interval in this context.

c) Carefully explain what "95% confidence" means.

Exercise 18

Depression. A study published in the Archives of General Psychiatry in March 2001 examined the impact of depression on a patient's ability to survive cardiac disease. Researchers identified 450 people with cardiac disease, evaluated them for depression, and followed the group for 4 years. Of the 361 patients with no depression, 67 died. Of the 89 patients with minor or major depression, 26 died. Among people who suffer from cardiac disease, are depressed patients more likely to die than non-depressed ones?

a) What kind of design was used to collect these data?

b) Write appropriate hypotheses.

c) Are the assumptions and conditions necessary for inference satisfied?

d) Test the hypothesis and state your conclusion.

e) Explain in this context what your P-value means.

f) If your conclusion is actually incorrect, which type of error did you commit?