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UNDERSTANDING VARIABILITY IN TIME SPENT IN SELECTED LOCATIONS FOR 7-12 YEAR OLD CHILDREN
Citation:
Xue, J, T R. McCurdy, J. D. Spengler, AND A H. Ozkaynak. UNDERSTANDING VARIABILITY IN TIME SPENT IN SELECTED LOCATIONS FOR 7-12 YEAR OLD CHILDREN. JOURNAL OF EXPOSURE ANALYSIS AND ENVIRONMENTAL EPIDEMIOLOGY 14(3):222-233, (2004).
Impact/Purpose:
The two main objectives of this research are (1) to improve and update and (2) to analyze the CHAD database.
For objective 1, we will
* Reconfigure the CHAD program into a completely modularized Oracle database.
* Redesign User Interface for effcient utilization of the program's capability.
* Obtain dates for those surveys that did not provide them to us, so that we can obtain associated meteorological/climatic inputs for the person-days of information without them.
* Revise the upper and lower bound delimiters in the energy expenditure distributions used for activity-specific estimates.
For objective 2, we will
* Evaluate data quality.
* Evaluate trends and activities for various subgroups.
* Identify temporal patterns for longitudinal data.
* Characterize resolution required for output for exposure and dose models.
Description:
This paper summarizes a series of analyses of clustered, sequential activity/location data collected by Harvard University for 160 children aged 7-12 in Southern California (Geyh et al., 2000). The main purpose of the paper is to understand intra- and inter-variability in the time spent by the sample in the outdoor location, the location exhibiting the most variability of the ones evaluated. The data were analyzed using distribution-free hypothesis-testing (K-S tests of the distributions), generalized linear modeling techniques, and random-sampling schemes that produced "cohorts" whose descriptive statistical characteristics were evaluated against the original dataset. Most importantly, our analyses indicate that subdividing the population into appropriate cohorts better replicates parameters of the original data, including the interclass correlation coefficient (ICC), which is a relative measure of the intra- and inter-individual variability inherent in the original data. While the findings of our analyses are consistent with previous assessments of "time budget" and physical activity data, they are constrained by the rather homogeneous sample available to us. Due to a general lack of longitudinal human activity/location data available for other age/gender cohorts, we are unable to generalize our findings to other population subgroups.
The analyses reported here were undertaken by staff scientists of the US Environmental Protection Agency and the Harvard School of Public Health. Its content is soley the responsibility of the authors and does not necessarily represent the official views of either organization or the funding sources mentioned below. It has been subjected to Agency and outside peer review and approved for publication. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.