Determine which chi-square test is appropriate in each of the following settings. Explain your reasoning.

a. Does chocolate help heart-attack victims live longer? Researchers in Sweden randomly selected 1169 people who had suffered heart attacks and asked them about their consumption of chocolate in the previous year. Then the researchers followed these people and recorded whether or not they had died within 8 years.

b. Random-digit-dialing telephone surveys used to exclude cellphone numbers. If the opinions of people who have only cell phones differ from those of people who have landline service, the poll results may not represent the entire adult population. The Pew Research Center interviewed separate random samples of cell-only and landline telephone users who were less than 30 years old and asked them to describe their political party affiliation.