How Much Observation Is Enough? Refining the Administration of SOPARC

in Journal of Physical Activity and Health
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The Systematic Observation of Play and Recreation in Communities (SOPARC) was designed to estimate the number and characteristics of people using neighborhood parks by assessing them 4 times/day, 7 days/week. We tested whether this schedule was adequate and determined the minimum number of observations necessary to provide a robust estimate of park user characteristics and their physical activity levels.


We conducted observations every hour for 14 hours per day during 1 summer and 1 autumn week in 10 urban neighborhood parks: 2 each in Los Angeles, CA; Albuquerque, NM; Columbus, OH; Durham, NC; and Philadelphia, PA. We counted park users by gender, age group, apparent race/ethnicity, and activity level. We used a standardized Cronbach’s alpha and intraclass correlation coefficients to test the reliability of using fewer observations.


We observed 76,632 individuals, an average of 547/park/day (range 155−786). Interobserver reliability ranged from 0.80 to 0.99. Obtaining a robust estimate of park user characteristics and their physical activity required a schedule of 4 days/week, 4 times/day.


An abbreviated schedule of SOPARC was sufficient for estimating park use, park user characteristics, and physical activity. Applying these observation methods can augment physical activity surveillance.

Cohen is with the Dept of Health, RAND Corporation, Santa Monica, CA. Setodji is with the Dept of Statistics, RAND Corporation, Santa Monica, CA. Evenson is with the Dept of Epidemiology, University of North Carolina at Chapel Hill. Ward is with the School of Physical Activity and Educational Services, Ohio State University, Columbus, OH. Lapham is with the Behavioral Health Research Center of the Southwest, Albuquerque, NM. Hillier is with the Dept of City and Regional Planning, University of Pennsylvania, Philadelphia, PA. McKenzie is Professor Emeritus, School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA.