Question
The table below presents childhood leukemia rates per 100,000 person-years by radon exposure status and air pollution exposure:
Exposed to radon
|
Not exposed to radon
| |
High air pollution exposure
|
601.6
|
58.4
|
Low air pollution exposure
|
127.3
|
11.3
|
a. Calculate the rate ratio for the association between radon exposure and leukemia within those exposed to high air pollution and within those exposed to low air pollution. Are the rate ratios approximately constant across categories of air pollution exposure?
b. Calculate the rate difference (attributable rate) for radon exposure within those exposed to high air pollution and within those exposed to low air pollution. Are the rate differences approximately constant across categories of air pollution?
c. Comment on the effects of the scale (additive versus multiplicative) on the assessment of effect measure modification (interaction).
d. The investigators wish to make a causal statement about whether air pollution exposure affects the association between radon and childhood leukemia. Which comparison (IDR or IDD) do you recommend they use and why?
Source: 250B Problem Set
