3.6 Statistics: In order to have an adequate number of node positive patients to test sensitivity an overall total of 240 patients is required. The proportion of patients who are node positive is estimated to be 0.35. A sample of 240 is expected to contain 84 node positive patients and the probability that at least 72 of the 240 patients are node positive is 0.95. The subsample of 72 node positive patients is sufficient to perform a one-sided test of equivalence for a target sensitivity of 0.80 and an allowable difference of 0.10 with significance level of 10% and power of 80%.The 168 node negative patients from the 240 total permit a one-sided test of equivalence for which the target specificity is 0.95 and the allowable difference is 0.05 with significance level of 5% and power of 90%.43