2.5. Statistical Analysis

All statistical analyses were performed using the SPSS software package version 18.0 for Windows (IBM Corporation, Armonk, NY, USA). The level of noise exposure during the break period (preparation and lunch hours) was determined by DOSE (%) measured using a noise dosimeter with a threshold (TL) of 80 dBA. The value of L_AVG was calculated using the measured time period (in hours) and DOSE (%) for each measurement classified by characteristics (work environment, department, employment type, or job task). The paired t-test was also performed to compare the L_AVG values for the same measurements during different sampling timetables with or without the break periods. The paired t-test and McNemar test were applied to compare the noise exposure levels measured using the different approaches of the Korean and OSHA’s hearing conservation program (HCP) by characteristics. Finally, the intraclass correlation coefficients (ICCs) were calculated to compare the average levels of occupational noise with the OEL values of 90 dBA (8 h) and 89.2 dBA (9 h) by decreasing 1 h for daily exposure sampling timetables from the beginning to the end of exposure sampling, and the McNemar test was performed to determine the most relevant timetable among the different sampling timetables with p-values at a significance level of 0.05.