Sample size analysis.

Our journal club enjoyed Nataraja et al.'s randomized trial: lavage vs suction in laparoscopic appendicectomies [ [1] Nataraja R.M. Panabokke G. Chang A.D. et al. Does peritoneal lavage influence the rate of complications following pediatric laparoscopic appendicectomy in children with complicated appendicitis? A prospective randomized clinical trial. J Pediatr Surg. 2019; 54: 2524-2527https://doi.org/10.1016/j.jpedsurg.2019.08.039 Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar ]. Section 1.4.1 considered two distributions (means 4.4 and 5.5 days, sd 1.29), and asked how large, equal sized, samples needed to be such that the chance of getting a p-value > 0.05 was about 20%:— this being the chance of making a Type II error, of wrongly accepting the null hypothesis when the parent populations differ. The Type II error is less well understood than the Type I error, represented by the p-value, being the chance of wrongly rejecting the null hypothesis when there is no difference between the parent populations. The authors determined a need for 50 patients in each sample; we disagree.