This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Case Control Study, Combined Designs, Subject name: Social & Preventive Medicine
Strength of association is given by 
Select and explain. 
A. p-value, B. Coefficient of regression, C. Alpha value, D. Odds ratio
D: Odds ratio
Answer: D: Odds ratio 
Explanation: Strength of association is given by Odds ratio or Cross product ratio in a Case control study. Odds ratio = ad/bc OR > 1 - Positive association, OR=1 - No association, OR < 1 - Inverse/ negative association. Chi-square test or t-test can only tell whether an association is statistically significant based on p-value, but doesn't give the magnitude of strength of association.