III. Proof of assertion regarding a mean: unknown 1. In a promotion competition in Ireland the ages of unsuccessful applicants and those who were successful in obtaining promotion were studied. For unsuccessful applicants, a sample of 23 was used, which reflected a mean age of 47 and standard deviation of 7.2. The sample of those who were successful showed a mean of 43.9 , with a standard deviation of 5.9 , in 30 cases analyzed. Use the .05 level of significance to test the claim that unsuccessful applicants come from a larger mean population than successful applicants