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A Measurement Error Model for Physical Activity Data (302561)

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Keywords: Survey methods, calibration, energy expenditure, obesity

As obesity-related disease rates increase, so has the interest in measuring the population's physical activity level. Of particular interest is an individual's "usual" or long-run average physical activity behavior as it relates to chronic diseases. Epidemiologists and physical activity researchers who are interested in estimating this quantity often do so with self-report activity logs that are prone to error, but do not take this into account when computing estimates. Using data composed of concurrent self-report and monitor readings on individuals, we develop models to measure the various sources of error in both devices. We also offer a method to estimate the usual activity distribution for a population through a measurement error model procedure. Finally, visualizations of model parameters are offered to impress upon practitioners the importance of taking measurement error into account when drawing conclusions from their studies.