<qa>  What is the reoperation rate for burr hole craniostomy?Study analysis Sample size calculation Power and sample size estimations are based on data from the literature indicating that the reoperation rate at 40 days for burr hole craniostomy or twist drill craniotomy ranges from 25 to 15 control groups, and our assumption that minicraniotomy would decrease the reoperation rate at 40 days to 5. In a test for trend in proportions, sample sizes of 49, 49, and 49 are obtained from 3 groups with proportions equal to 0.25, 0.15, and 0.05. The total sample of 147 subjects achieves 81 power to detect a linear trend using a two-sided Z test with continuity correction and a significance level alpha of 0.05. 