  While there is wide agreement that physical activity is an important
component of a healthy lifestyle, it is unclear how many people adhere to
public health recommendations on physical activity. The Physical Activity
Guidelines (PAG), published by the CDC, provide guidelines to American adults,
but it is difficult to assess compliance with these guidelines. The PAG further
complicate adherence assessment by recommending activity to occur in at least
10 minute bouts. To better understand the measurement capabilities of various
instruments to quantify activity, and to propose an approach to evaluate
activity relative to the PAG, researchers at Iowa State University administered
the Physical Activity Measurement Survey (PAMS) to over 1,000 participants in
four different Iowa counties. In this paper, we develop a two-part Bayesian
measurement error model and apply it to the PAMS data in order to assess
compliance to the PAG in the Iowa adult population. The model accurately
accounts for the 10 minute bout requirement put forth in the PAG. The
measurement error model corrects biased estimates and accounts for day to day
variation in activity. The model is also applied to the nationally
representative National Health and Nutrition Examination Survey.
