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Table 1 Sample size calculations

From: Pay-it-forward gonorrhea and chlamydia testing among men who have sex with men in China: a study protocol for a three-arm cluster randomized controlled trial

Pay-it-forward and standard of care ICC 0.01 0.05
Proportion in control group 0.06 0.06
Superiority margin 0.2 0.2
Proportion in intervention group assuming H0 0.26 0.26
Proportion in intervention group assuming H1 0.54 0.54
Difference at which power is calculated 0.48 0.48
Number of people per cluster 10 10
Alpha 0.05 0.05
Power 0.8 0.8
Total sample size per arm 30 40
Number of clusters per arm 3 4
Pay-what-you-want and standard of care ICC 0.01 0.05
Proportion in control group 0.06 0.06
Superiority margin 0.2 0.2
Proportion in intervention group assuming H0 0.26 0.26
Proportion in intervention group assuming H1 0.42 0.42
Difference at which power is calculated 0.36 0.36
Number of people per cluster 10 10
Alpha 0.05 0.05
Power 0.8 0.8
Total sample size per arm 80 110
Number of clusters per arm 8 11
  1. ICC Intra-class correlation