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Non-smokers

Smokers

 

CAD

No CAD

CAD

No CAD

 

High coffee

40

90

High coffee

150

65

 

Low coffee

65

150

Low coffee

45

20

 

(a)  Calculate the crude odds ratio (for the association of coffee drinking and CAD) and the two stratum-specific odds ratios. Show your calculations. (3 pts)

(b) Next assess whether: 

i.  smoking is related to coffee consumption among those without CAD.

ii.  smoking is related to CAD among subjects with low coffee consumption

 Show the new 2×2 tables for these relationships and your calculations for the stratum specific ORs for the new tables. (4 pts)

(c) If you knew nothing else about this clinical/biological system, are the data given in the question and your calculations in item (b) sufficient evidence for you to conclude that smoking is a confounder in the relationship between coffee use and CAD? Explain the rational behind your answer.