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Table 2 The average and (5th percentile) of the proportion of negative Δ’s as a function of the coefficient of variation and the number of clinical centers

From: Accounting for treatment by center interaction in sample size determinations and the use of surrogate outcomes in the pessary for the prevention of preterm birth trial: a simulation study

Coefficient of variation Probability that π Si  > 0.225 Number of clinical centers
20 40 60 80 100
0 1 0.98 (0.88) 0.99 (0.94) 0.98 (0.93) 0.99 (0.93) 0.99 (0.94)
0.1 0.99 0.98 (0.87) 0.98 (0.92) 0.99 (0.92) 0.98 (0.92) 0.99 (0.94)
0.2 0.90 0.97 (0.88) 0.97 (0.85) 0.98 (0.90) 0.98 (0.90) 0.99 (0.92)
0.3 0.79 0.97 (0.87) 0.96 (0.79) 0.97 (0.85) 0.98 (0.87) 0.98 (0.90)
0.4 0.71 0.97 (0.86) 0.94 (0.73) 0.96 (0.79) 0.97 (0.85) 0.98 (0.89)