Part III: Measuring hearing-critical job tasks 139 ambient noise of six different train types. For this experiment, the signal detection test was conducted twice in all driving conditions, with a 15-minute break separating the two sessions. The order of the driving conditions was counterbalanced using Latin squares (Wagenaar, 1969). The first author was the test leader for all subjects. Statistical analysis The Intraclass Correlation Coefficient (ICC) was used to assess reliability since this measure assesses the strength of the correlation while taking into account possible systematic differences (Koo & Li, 2016). When comparing the size of this correlation coefficient to Pearson coefficients, one should take into account that generally, the ICC coefficients are smaller than Pearson coefficients. ICCs were calculated for all driving conditions to assess the test-retest reliability using an ICC 2-way mixed-effects model with an absolute agreement definition (De Vet et al., 2006). The interpretation was as follows: below 0.50, poor; between 0.50 and 0.75, fair; between 0.70 and 0.90 good; above 0.90, excellent (Perinetti, 2018). Further, we calculated the mean difference between the test and the retest measurements and the SD of this difference. We calculated the standard error of measurement (SEM) using the formula SD * √(1-R), with R equal to ICC and SD equal to √(total variance). The smallest detectable change (SDC) was calculated as an indication of measurement error using the formula 1.96 * √2 * SEM. Data organization and the statistical analysis were performed using the Statistical Package for Social Sciences version 25.0 (Armonk New York USA). Experiment 2 The purpose of experiment 2 was to assess the construct validity of the signal detection test. Therefore, we identified locomotive engineers who performed their auditory fitness for job assessment at the Amsterdam UMC. They underwent a job assessment because they were suspected of being hearing impaired. These engineers performed the signal detection test in four driving conditions in addition to the conventional hearing tests that are required to pass the auditory fitness for job assessment.
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