Fig. 1From: Determining sample size for progression criteria for pragmatic pilot RCTs: the hypothesis test strikes back!Illustration of power using the 1-tailed hypothesis testing against the traffic light signalling approach to pilot progression. E, observed point estimate; RUL, upper limit of RED zone; GLL, lower limit of GREEN zone; Ac, cut-off for statistical significance (at the 1-sided 5% level); α, type I error; β, type II errorBack to article page