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Table 1 Enrollment and completion rates of Tiers I, II, and III

From: Study of Use of Products and Exposure-Related Behaviors (SUPERB): study design, methods, and demographic characteristics of cohorts

  Targeted enrollment; (% recruited northern, central) Actual enrollment (northern, central) Full data completion (northern, central) Only partial data completion (northern, central) Only minimal data completion (northern, central)
Tier I: year 1 only    5 survey elements 3-4 survey elements 1-2 survey elements
  n = 750 n = 655 n = 580 n = 31 n = 39
  (26%,32%) (499, 156) (87%,95%) (6%,2%) (7%,3%)
Tier I: longitudinal (years 1-3)    3 years 2 years ≤1 year
  See above See above n = 252 n = 182 n = 221
    (38%,41%) (25%,37%) (37%,22%)
Tier II: 15/18 monthsa    15-18 monthly surveys 10-14 monthly surveys 1-9 monthly surveys
  n = 250 n = 250 95b 26 129
  (77%,75%) (186, 64) (29%,63%) (11%,9%) (60%,28%)
Tier III: 8 visits over 4 seasonsb    4 collection periodsc 2-3 collection periods 1 collection period
  n = 40 n = 47 n = 40 n = 4 n = 3
  (34%,52%) (30, 17) (90%,76%) (7%,12%) (3%,12%)
  1. a Full completion depended upon timing of enrollment into tier 2 as it was modified from 15 to 18 months.
  2. b Includes participants (n = 53) who attempted to complete surveys but encountered issues with the internet survey.
  3. c Each collection consisted of a set-up visit and a take-down visit at the beginning and end of a week. The goal was for four collection periods across a 16 month period.