Letter to the editor

Scand J Work Environ Health Online-first -article    pdf

doi:10.5271/sjweh.3824

Determining an optimal minimum number of subjects in each occupation for a job exposure matrix (JEM) using self-reported data: a missing test

by Choi BK

I read with great interest the paper by Hanvold et al (1) about the construction and evaluation of a gender-specific job exposure matrix (JEM) of mechanical and psychosocial work exposures using a Norwegian national survey data. I have found one significant methodological issue in the paper. In addition, I would like to discuss an important knowledge gap in the literature that the paper by Hanvold et al exposes.

The authors said that “…Earlier studies recommend 10 subjects in each group to achieve a reliable estimation of exposures, however, we used a minimum of 19 in each occupational group to increase the reliability of the estimates.” The earlier study referred to here is that of Le Moual et al (2). However, like other investigators (3), the authors have misunderstood this paper. Le Moual et al did not make any recommendation for a minimum number of subjects in each occupation for creating a JEM. In fact, Le Moural et al (2) constructed their JEMs with 2, not 10 subjects, as the minimum number of subjects in each occupation (see a note in table 1: one exclusion criterion for their JEM was “occupations

This article refers to the following texts of the Journal: 1993;19(1):21-28  2019;45(3):239-247