More than 95% of the total worker population was routinely
exposed to noise levels at or above 85 dB, the standard
set by OSHA for inclusion in an Hearing Conservation Program
(USDL, 1983). According to data provided by the
plant, the mean noise exposure for workers was 92 dB.
Effectiveness of Tailored Intervention
Total Sample Use of HPDs was recorded as a percentage of
time where 0% equaled “no use” and 100% equaled “use of
HPDs whenever they were required.” Paired t tests (twosided)
determined the significance of pretest to posttest
changes in mean use. Repeated measures analysis of variance
(ANOVA) established whether change from pretest to
posttest mean use differed by the three types of intervention
(tailored [n = 446], nontailored predictor-based [n = 447],
and control [n = 432]). The dependent variable (mean use of
HPDs), was calculated as the mean of self-reported use during
the past week and the past month.
Various assumptions of the analyses were examined.
The data had a moderate negative skew (-1.40) but
because of the large sample size and the Central Limit Theorem,
this was not a problem. Variances were similar in the
three groups. Finally, because there were only two measurement
points (pre and post) the sphericity assumption