You may use OpenEpi for all statistical calculations.

1. Suppose a case-control study of the was performed to assess the relationship between alcohol consumption (ALC) and oral cancer (OCa) among non-smokers. Results of this study, stratified on age, are displayed below:

 Age 40-49 ALC No ALC OCa 4 25 No OCa 22 309

 Age 50-59 ALC No ALC OCa 12 10 No OCa 37 67

 Age 60+ ALC No ALC OCa 11 12 No OCa 31 67

a. What is the crude odds ratio for these data?

b. What are the stratum-specific ORs. Is there evidence of effect modification by age? Justify your answer.

c. What is the value of the mOR and 95% CI? Based on this summary estimate, is there evidence of data-based confounding by age in these data? Justify your answer.

d. Based on the results above, which do you think it is better to present: the crude OR, the stratum-specific ORs or the mOR?

e. Carry out the appropriate test to determine whether the observed overall association between ALC and OCa, stratified on age, is statistically significant. Report the results of the appropriate chi-square test.

2. A case-control study was conducted to assess the potential relationship between alcohol consumption and bladder cancer. Data from the study are summarized below, stratified on three race categories.

 White ALC No ALC Case 72 41 Control 106 105

 Black ALC No ALC Case 93 54 Control 113 113

 Asian ALC No ALC Case 68 33 Control 78 142

a. What is the crude OR for these data?

b. Calculate the stratum-specific ORs. Is there evidence of effect modification by race? Justify your answer.

c. Should you estimate an overall adjusted odds ratio that controls for race using all three strata? Justify your answer.