Based on a previous study which reported a prevalence of low
back pain among rubber tappers of 55%, with a small design effect
due to systematic random sampling of 1.2 and an estimated nonresponse
rate of 10% that is usually used for field survey, the
required sample size was 502 subjects. This sample size is also
enough to test the hypothesis with a significance level of 0.05
which estimates that low back pain was 45% among an abnormal
ergonomic exposure group and 36% among a non-exposure group.
Due to no existing study of risk factors for low back pain among
rubber tappers, we estimated the prevalence of low back pain