Objectives:In a climate of scarce research funds, cost-effective exposure assessment becomes more critical. There is a long-acknowledged tradeoff between precision and cost of exposure assessment methods (Winkel and Mathiassen, 1994) that is seldom quantified.The purpose of this study was to compare different sampling strategies for observed trunk posture and determinewhich is the most cost-effective.Knowing the price-performance tradeoffs of observational exposure assessment can help researchers make the most of limited funds.Methods(maximum 150 words)Trunk posture data was observed by trained experts during full work shifts on 126 workers in heavy industry, with repeated measures on 76% of workers. The observed percentage of time spent with trunk flexed more than 60 degrees was recorded and summarized for each work day using the Back-EST sampling method (Village et al 2009). A cost model was developed using previously published cost data (Trask et al 2007) to account for the costs of recruiting companies, workers, and making a full-shift observation of trunk posture. Precision was described in terms of the standard error of the group mean (SEM), using equations from Samuels (1985) that account for multiple measures within companies and workers. Changes in cost efficiency were calculated for sampling strategies employing different combinations of the following: 1-4 companies, 1-12 workers, and 1-4 measures per worker. The case of one recruited company is highlighted here as an example.Results:(maximum 100 words)The SEM declines steeply for the first few additional subjects, while further subjects increase costs considerably with no substantial improvements in precision. Adding repeated measures generally increased costs with smaller gains in precision. In a single-company example, measuring 6 subjects twice (12 measurements total) yields SEM = 0.76 and costs $3929. The same number of measurements can cost up to $4505 with 12 subjects and no repeats, improving the SEM to 0.75. However, increased cost does not always deliver gains in precision; an SEM of 0.76 can cost up to $5545 when 5 subjects are measured 4 times.Conclusions(maximum 100 words)The total number of measurements has been used as a metric for cost optimization in previous investigations (Lemasters et al 1996). However, an equal number of measurements can have different costs depending on how they are allocated due to recruitment costs. Such cost-efficiency information allows researchers to make informed decisions on the use of limited resources when designing ergonomic studies; either determining the maximum precision level that can be achieved for a given cost, or the minimum cost for a given level of precision.