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Table 2 Baseline characteristics of the gift voucher trial

From: The effect of two lottery-style incentives on response rates to postal questionnaires in a prospective cohort study in preschool children at high risk of asthma: a randomized trial

  Gift Voucher No Gift Voucher Total
N 389 382 771
Male, n (%) 230 (59.1) 202 (52.9) 432 (56)
Age yrs, mean (SD)* 2.22 (1.2) 2.33 (1.3) 2.27 (1.2)
Nr of symptoms at onset, N (%)
1 ** 263 (67.6) 255 (66.8) 518 (67.2)
2 *** 94 (24.2) 101 (26.4) 195 (25.3)
3 **** 32 (8.2) 26 (6.8) 58 (7.5)
Nr of Questionnaires #
2 13 (3.3) 25 (6.5) 38 (4.9)
3 38 (9.8) 46 (12.0) 84 (10.9)
4 338 (86.9) 311 (81.4) 649 (84.2)
Level of education of parents, N (%)
Lowest 11 (2.8) 5 (1.3) 16 (2.1)
Low 66 (17.0) 51 (13.4) 117 (15.1)
Medium 149 (38.3) 141 (36.9) 290 (37.6)
High 141 (36.3) 156 (40.8) 297 (38.5)
No information 22 (5.7) 29 (7.6) 51 (6.6)
Allergy or asthma parents
At least one parent with allergy or asthma 223 (57.3) 229 (59.9) 452 (58.6)
No information 21 (5.4) 27 (7.1) 48 (6.2)
Ethnicity of parents
Western 120 (30.9) 108 (28.3) 228 (29.6)
Non-western 199 (51.2) 188 (49.2) 387 (50.2)
No information 70 (18.0) 86 (22.5) 156 (20.2)
  1. * Range of age 1–5 in all groups.
  2. **Cough or wheeze or shortness of breath.
  3. *** Cough & wheeze or cough & shortness of breath or wheeze & shortness of breath.
  4. **** Cough & wheeze & shortness of breath.
  5. # Depending on age at onset, a participant was intended to fill in 2, 3 or 4 questionnaires.
  6. Table 1 shows the baseline characteristics of the comparison groups of the daytrip trial and Table 2 of the gift voucher trial.