Group-based measurement strategies in exposure assessment explored by bootstrapping

Area of Science:

• Occupational health and safety
• Ergonomics
• Industrial hygiene

Background:

• Assessing worker exposure to physical tasks like pushing is crucial for workplace safety.
• Understanding the precision of group mean exposure estimates is key for effective risk management.

Observation:

• Onsite observations were used to record the frequency and duration of pushing for two occupational groups.
• Data were segmented into 30-minute observation periods.
• Bootstrapping methods generated 90% confidence intervals to quantify the precision of group mean exposure.

Findings:

• Little precision was gained by observing more than 10 workers, with confidence intervals decreasing by less than 5% per additional worker after this threshold.
• When workers were observed for only 4 periods, an additional 4 workers were needed to maintain precision.
• An unbalanced observation strategy (approx. 8 periods/worker) minimally impacted group mean precision.

Implications:

• The number of workers observed and the number of measurements per worker significantly influence the precision of group-based mean exposure.
• Measurement strategies should proactively consider potential variance sources and assess exposure variability for accurate risk assessment.