Many investigators have studied the relationship between asbestos exposure and death from chronic obstructive pulmonary disease (COPD). 1) Suppose that among workers exposed to asbestos in a shipyard...

Many investigators have studied the relationship between asbestos exposure and death from chronic obstructive pulmonary disease (COPD).

1) Suppose that among workers exposed to asbestos in a shipyard in 1980, 33 died over a 10 year period from COPD, whereas only 24 such deaths would be expected based on statewide mortality rates. Is the number of deaths from COPD in this group excessive?

2) Twelve case of leukemia are reported in people living in a particular census tract over a 5 year period. Is the number of cases abnormal if only 6.7 cases would be expected based on national cancer-incidence rates?