Question

1. To investigate the association between ascariasis and hand wash investigators conducted a case-control study with 100 cases (100 children with stool-test Positive) and 100 controls (100 children Negative). Among Positives children, 50 gave a history of exposure (frequent hand washes). Among those Negatives, 25 gave a history of exposure to hand washes.

 For this study, calculate the odds ratio & interpret the result.

Answer 1

To calculate the odds ratio (OR) for the association between ascariasis and hand washing in this case-control study, we can use the following formula:

OR = (a/c) / (b/d)

Where:

a = number of cases with exposure (frequent hand washing) = 50

b = number of cases without exposure (not frequent hand washing) = 50

c = number of controls with exposure (frequent hand washing) = 25

d = number of controls without exposure (not frequent hand washing) = 75

Plugging in these values into the formula:

OR = (50/25) / (50/75)

OR = 2

This means that the odds of having ascariasis among children who frequently wash their hands are 2 times higher than the odds of having ascariasis among children who do not frequently wash their hands.

In terms of interpretation, an OR of 2 means that frequent hand washing is associated with a twofold increase in the odds of having ascariasis. However, it should be kept in mind that this association does not necessarily imply causality, and other factors might be involved. Additionally, the study design of a case-control study may have its own limitations, such as recall bias or selection bias, so it would be important to consider these factors when interpreting the results.

I hope this helps :)