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Table 2 PA within- and between-person variance and number of days to assess habitual PA, total (N = 50)

From: Variability and reliability study of overall physical activity and activity intensity levels using 24 h-accelerometry-assessed data

    Percent of total variance  
PA parametera Within-person variance Between-person variance Within-person variance Between-person variance Number of days
  sw2 sb2 sw2 sb2 Db
Overall PA, cpm 0.09593 0.06317 60.3 39.7 7
Time in inactivity, min/d 0.00273 0.00225 54.9 45.1 6
Time in low intensity activity, min/d 0.06727 0.05627 54.5 45.5 6
Time in moderate activity, min/d 0.09604 0.05033 65.6 34.4 9
Time in vigorous activity, min/d 0.28890 0.21890 56.9 43.1 6
Time in very vigorous activity, min/d 0.57190 0.34590 62.3 37.7 8
  1. cpm counts per minute, D number of days to assess physical activity based on a given r (assumed correlation between observed and true mean of physical activity parameter) [19], PA physical activity, s b 2 between-person variance over 11 days of physical activity, s w 2 within-person variance over 11 days of physical activity
  2. aall analyses were performed using log-transformed data
  3. bD is calculated based on an assumed correlation between observed and true mean physical activity of r = 0.9 and is rounded up to the nearest full number of days