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Table 1 Sample size calculation for the required number of subjects in each treatment group (double sided).

From: A multi-centre randomized controlled trial comparing electrothermal arthroscopic capsulorrhaphy versus open inferior capsular shift for patients with shoulder instability: Protocol implementation and interim performance: Lessons learned from conducting a multi-centre RCT [ISRCTN68224911; NCT00251160]

Alpha level("p" value) Power
  60% 70% 80% 90%
0.10 12 15 20 27
0.05 16 20 25* 33
0.01 25 30 37 47
0.001 40 46 54 65
  1. N per group = 25* Expected dropout 12% 25/.88 = 28.4 Total per group 29 Grand Total 58 patients