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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)