Sample Size Estimation:
The sample size for this study was determined according to the
objectives of the study. Objective 1: to determine the quality of life
among the quarry workers. Sample size was determined using single
proportion formula as follows: N= p (1-p)(Z/E)2 N=
sample size, p= proportion of “very poor quality of life” in
population, Z= standard normal distribution, E=precision, Where p=0.5
(Mazlan et al.,) [8], Z= 1.96 and E= 0.06. n=
0.5(1-0.5)(1.96/0.06)2.
Therefore n= 0.25X32.67X32.67. N=266 respondents.
Objective 2: to determine the sociodemographic and workplace
determinants of quality of life among quarry workers. The sample size
was calculated using PS software. Alpha = 0.05, power =0.8, m = 1, P0 =
0.50 (Mohammad et al., 2018), P1 = 0.75 (expert opinion), sample size =
174 (Dissatisfied/poor QOL = 116, Satisfied/good QOL=58). P0 =
probability of exposure to the risk (WRMSDs) in controls (good QOL) OR
WRMSDs / quarry workers. P1 = probability of exposure to the risk
(WRMSDs) in cases (poor QOL).
Therefore, the largest sample size for this study was 266 respondents as
shown in objective 1 above.