Justification: If the true minimum difference (or Minimal Clinically Important Difference) between the experimental and control group KT-1000 measurement means is 0.6mm the researchers will need to recruit 60 cases in each group to be able to reject the null hypothesis that the population means are equal with probability (power) 0.9, type I error rate of 5% (significance) and mean SD of 1.0 (Lanzetti paper referred to above) An adjustment of 20% to account for drop outs would increase the number in each group to 75 and the total sample size to 150 cases.