Final answer:
The odds ratio of a SNP in a case/control study is calculated by using a 2 x 2 table to compare the odds of exposure in cases versus controls and is not computed by merely dividing or multiplying the number of cases by controls, or taking a square root.
Step-by-step explanation:
The odds ratio of a SNP in a case/control study is calculated by comparing the odds of exposure in cases to the odds of exposure in controls. The process involves constructing a 2 x 2 table with the SNP variant and disease status (case or control). You then calculate odds ratio (OR) as (odds of exposure in cases) / (odds of exposure in controls), which equates to (a/c) / (b/d) where 'a' and 'b' are the number of cases with and without the SNP, respectively, and 'c' and 'd' are the number of controls with and without the SNP, respectively. Answer d) 'Compute the square root of cases divided by controls' is not the correct method for calculating an odds ratio.
For example, if 100 cases have the SNP and 50 do not, and among the controls, 40 have the SNP and 60 do not, the OR would be (100/50) / (40/60) = 2/0.66 ≈ 3.03.