# 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?

## Solution

Robert answered on Dec 20 2021
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 state wide mortality
ates. Is the number of deaths from COPD in this group excessive?

Solution:

Here number of event and time matters to decide whether the number of deaths from COPD in this
group excessive or not. There are 9 deaths more than the expected value and the percentage of
death increased by 100*(33-24)/24 = (9/24)*100 = 37.5% increase in the deaths which is high. So
we...
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