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Table 2 Prevalence of registration among published randomized trials according to trial size

From: Registration of published randomized trials: a systematic review and meta-analysis

Reference Sample size Number of trials Number of registered trials Proportion of registered trials (95% CI) p value*
Jones [48] < 100 48 17 0.35 (0.22; 0.51) 0.009
100–199 36 14 0.39 (0.23; 0.57)
200–499 30 21 0.70 (0.51; 0.85)
≥ 500 9 5 0.56 (0.21; 0.86)
Mann [53] < 100 71 33 0.46 (0.35; 0.59) 0.0009
100–499 117 83 0.71 (0.62; 0.79)
500–999 13 10 0.77 (0.46; 0.95)
≥ 1000 15 12 0.80 (0.52; 0.96)
McGee [54] < 200 235 40 0.17 (0.12; 0.22) < 0.0001
≥ 200 72 34 0.47 (0.35; 0.59)
Pinto [61] ≤ 25 34 5 0.15 (0.05; 0.31) < 0.0001
26–50 53 13 0.25 (0.14; 0.38)
51–100 61 19 0.31 (0.20; 0.44)
101–499 42 23 0.55 (0.39; 0.70)
≥ 500 10 7 0.70 (0.35; 0.93)
Reveiz [62] ≤ 100 442 59 0.13 (0.10; 0.17) < 0.0001
> 100 84 30 0.36 (0.26; 0.47)
  1. *Chi-squared test for trend in proportions in studies with three or more categories or chi-squared test for studies with two categories