STAT 110: Group Exercise Name: ________________
Suppose the proportion of deaths due to lung cancer for males aged 15-64 in England
and Wales is 12%. Of interest is whether or not workers from a chemical plant have a
statistically higher risk of having lung cancer. Over the study period, there were 20
workers from the chemical plant in this age group that died. Four of these were found
to have lung cancer.
1. How many of the 20 deaths would we expect to be from lung cancer if the chemical
plant workers death rate due to lung cancer was similar to the greater population?
2. Do we have to observe the expected number exactly or are deviations from this
expected number acceptable? Discuss.
3. Using Excel, determine the individual and cumulative probabilities for Number of
Cases = 2 and Number of Cases = 4.
4. In this study there were 4 deaths from lung cancer. Is this larger than the expected
number? Does this lend support to the notation that “working in a chemical plant
may increase your chances of dying from lung cancer”?
5. Using the above probabilities, what is the chance of observing exactly 4 deaths from
lung cancer out of these 20 individuals?
6. What is the chance of observing 4 or more deaths from lung cancer out of these 20
7. Do the probabilities computed in problem 5 and 6 lend support to the notation that
“working in a chemical plant for at least one year may increase your chances of
dying from lung cancer”? When answering this question, use the standard error rate
8. What is an appropriate cutoff for this problem? That is, what is the number of
deaths from lung cancer for which we’d believe the risk of death from lung cancer
for those who work in this chemical plant is higher than the general population?