Some people who are having a heart attack do not experience chest pain, although most do. A study of people admitted to emergency rooms with heart attacks compared the death rates of people who had chest pains with those of people who did not have chest pains (Brieger et al. 2004). Of the 1763 people who had heart attacks without chest pain, 229 died, while of the 19,118 people who had heart attacks with chest pain, 822 died.

a. Test whether the presence or absence of chest pains during a heart attack is associated with the probability of death.

b. Give a valid estimate of the magnitude of the association between chest pain and risk of death. Put bounds on your estimate.