Q: A case control study is done to see association of smoking and oral cancer. 30 patients of oral cancer smoked while 20 did not smoke. Amongst the controls, 20 smoked and 30 were non-smokers. Odds ratio of getting oral cancer in smokers to that of non smokers is.

a) 0.44     

b) 1           

c) 1.5        

d) 2.25

 

 

 

 

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Ans: d) 2.25

 

Step 1: Make a 2x2 table with the given data. It will look as follows:

	Oral CA	Control	Total
Smoker	30	20
Non-Smoker	20	30
Total

 

Step 2: Use the formula for Odds Ratio:

Odds Ratio = ad/ bc  =  30x30 / 20x20        = 900 / 400        = 9/4     = 2.25