Researchers have been studying the association betweencigarette smoking and caffeine intake and
Parkinson's Disease for more than 40 years. The resultsof a study by Checkoway et al. (2002) follow:
Ever having smoked cigarettes resulted with an oddsratio (OR) = 0.5 (95% confidence interval (CI):
0.4, 0.8).
The OR for current smokers was OR = 0.3 (95% CI: 0.1,0.7).
Among ex-smokers the OR = 0.6 (95% CI: 0.4,0.9).
Interpret the three ORs (in your ownwords).
