05/04/2011

Theoretical and Empirical Efficiency of Sampling Strategies for Estimating Upper Arm Elevation

To investigate the statistical efficiency of strategies for sampling upper arm
elevation data, which differed with respect to sample sizes and sample
allocations within and across measurement days, the authors investigated
sixty-five sampling strategies.

They found the assumptions of independence and homoscedasticity in the
theoretical model to be violated, most notably expressed through an
autocorrelation between measurement units within working days. This study
demonstrates that when exposure data are autocorrelated within days-which we
argue is the major reason why theory overestimates sampling
performance-sampling efficiency can be improved by distributing the sample
widely across the day or across days, preferably using a fixed-interval
strategy. While this guidance is particularly valid when small proportions of
working days are assessed, we generally recommend collecting more data than
suggested by theory if a certain precision of the resulting exposure estimate
is needed. More data per se give a better precision and sampling larger
proportion(s) of the working day(s) also alleviate the negative effects of
possible autocorrelation in data.

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AplusA-online.de - Source: The Annals of Occupational Hygiene