 SAMPLE SIZE ASSESSMENT To compare two groups Intervention and Control using a two- sample, two-sided t-test with a 5 statistical significance level, the minimum number of evaluable PWDs required in each group is 470 940 overall, to give a power of 80. If there would be a drop-out rate of 20 of the PWDs then the number of PWDs registered on the study would need to be 564 in each group 1128 overall. 