Question

Smoking Status	Lung Cancer	No Lung Cancer	Total
Yes	100	300	400
No	500	500	1000

1. Calculate the risk of developing lung cancer among the exposed group
2. Calculate the risk of developing lung cancer among the unexposed group
3. Calculate the risk ratio of the exposed group when compared to the unexposed group
4. Calculate the odds of developing lung cancer among the diseased group
5. Calculate the odds of developing lung cancer among the non- diseased group
6. Calculate the exposure odds ratio
7. Interpret the exposure odds ratio

Answer 1

Smoking Status	Lung Cancer	No Lung Cancer	Total	Cumulative Incidence
Yes	100	300	400	25%
No	500	500	1000	50%
Total	600	800	1400	43%

a) Calculate the risk of developing lung cancer among the exposed group=100/(100+300)=100/400=0.25=25%

b) Calculate the risk of developing lung cancer among the unexposed group=500/(500+500)=500/100=0.5=50%

c) Calculate the risk ratio of the exposed group when compared to the unexposed group

The risk ratio is simply the ratio of these two risks=risk of developing lung cancer among the exposed group/risk of developing lung cancer among the unexposed group= 25/50=1/2=0.5

Thus, smoker were 0.5 times as likely to develop lung cancer as those who donot smoke.

d) Calculate the odds of developing lung cancer among the diseased group

odds(exposure) =(100/300)=100/300=1/3=0.333

e) Calculate the odds of developing lung cancer among the non- diseased group

odds(Non-exposure)=(500/500)=1

f) Calculate the exposure odds ratio=odds(exposure)/odds(Non-exposure)=(100/300)/(500/500)=1/3=0.333

g) exposure odds ratio is less than 1.0 means that the odds of exposure among lung cancer is lower than the odds of exposure among no lung cancer. The exposure may be protective against the disease.