Statistics: Testing Hypothesis with the Z-statistic – #17


Question: A case control study was done to investigate the association between tuberculosis and heavy smoking in a particular population. One question that arose was whether or not there was an interaction between age and smoking with respect to tuberculosis – that is, does the risk of tuberculosis due to smoking increase in older patients? The following data are available:

AGE NUMBER OF
CASES
PERCENT
HEAVY SMOKERS
NUMBER OF
CONTROLS
PERCENT
HEAVY SMOKERS
39 OR LESS
50 OR MORE
221
165
48.3%
51.0%
136
162
46.0%
40.1%

a) What is the association between smoking and tuberculosis among those aged 39 or less? What is the association between smoking and tuberculosis among those aged 50 or more?

b) Is there a significant difference between the two age groups with respect to the association between smoking and tuberculosis? Justify your answer.

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