On completion of data collection, results of the Laboratory Assessment Checklist pretest and posttest from the three
groups were analyzed using the SPSS version 11.0 computer statistical analysis program (SPSS, Inc., Chicago, IL). To
evaluate the change in body position and workstation design after the intervention, the total number of “correct” answers
on the Laboratory Assessment Checklist was used to calculate mean scores for all groups before and after intervention. To
account for variability, the standard deviation and standard error of measurement of pretest and posttest scores were calculated for each group. A one-way analysis of variance (ANOVA) was conducted to determine whether significant
differences were found across treatment groups in relation to demographic characteristics, injury or illness status, or perceived work comfort. Analysis of covariance (ANCOVA) was used to measure the differences among group means. This
technique has the ability to reduce the error variance in the outcome measure and allows the measurement of group differences (Ott, 1993). This type of analysis was used to determine whether the mean scores differed before and after intervention and whether the groups differed in the degree to which the mean score on the Laboratory Assessment Checklist improved. Statistical significance was established a priori at p < .05. To assess the magnitude of the change in scores, within and between group effect sizes also were calculated, using Cohen’s d and the distribution overlap (Cohen, 1988;Valentine & Cooper, 2003).