A case control study was conducted to investigate risk factors for malaria in a

Question

A case control study was conducted to investigate risk factors for malaria in a country in which the disease is endemic. In a preliminary analysis, the association between gender and malaria risk was investigated. These data are shown in the first table. a. Calculate a measure of association between gender and risk of malaria. Interpret this result. All Subjects Gender Male Female CasesControls 68 82 62 Mostly Outdoor Work Controls Gender Male Female Cases 53 10 15 Mostly Indoor Work Gender Male Female Controls Cases 35 52 53 79

Explanation / Answer

measure of association is calculated by odd ratio(OR)=ad/bc

ORall subject=(82*88)/(62*68)=1.71

ORoutdoor=(53*3)/(10*15)=1.06

ORindoor=(35*79)/(52*53)=1.00

for all the subject there is strong association ( OR value is more than 1) between gender and malaria but in indoor cases there is no association between gender and malaria as OR value is 1 . for outdoor cases there is moderalte association between gender and malaria ( OR value is more than 1)

An odds ratio is a relative measure of effect, which allows the comparison of the intervention group of a study relative to the comparison or placebo group.

So when researchers calculate an odds ratio they do it like this:

The numerator is the odds in the intervention arm

The denominator is the odds in the control or placebo arm = Odds Ratio (OR)

So if the outcome is the same in both groups the ratio will be 1, which implies there is no difference between the two arms of the study.

cases control group1 a b group1 c d

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