Question

Out of 300 randomly selected welders (W), 33 suffer from retinal damage (R). Out of 250 randomly slected non-welders (W^c), 20 suffer from retinal damage (R).

a) What is the relative risk of retinal damage (R) foor welders (W) verses non-welders (W^c)? Interpret.

b) What is the relative odds (odd ratio) of retinal damage (R) for welders (W) verses non-welders (W^c)? Interpret.

Answer 1

Exposed group: Welders

Unexposed group: Non-welders

a)

Relative risk is:

R = P(retinal damage in exposed group)/P(retinal damage in unexposed group)

where, P is the probability

Thus, R = (33/300)/(20/250) = 1.375

Interpretation:

The Welders (exposed group) are 1.375 times more likely to suffer from retinal damage than non-welders (unexposed group).

b)

Relative odds Ratio is:

OR = odds ratio of welders/odds ratio of non-welders

OR = [33/(300-33)] / [20/(250-20)] = (33/267)/(20/230)

0R = 1.42

Interpretation:

The Welders(exposed group) are 1.42 times more likely to have odds (presence of retinal damage to absence of retinal damage) than non-welders (unexposed group).