Example 5 One sample ttest The personnel department of a company developed an aptitude test for screening potential employees. The person who devised the test asserted that the mean mark attained would be 100. The following results were obtained with a random sample of applicants: X =96, 525.2, n=13. Test this hypothesis against the alternative that the mean mark is less than 100, at the 1% significance level. Given: u = 100?, X = 96, s = 5.2, n = 13. H0: 11 H: u Significance level (a): 1% (0.01) Critical Value: 0 unknown so ttables. 1% sig., 1 tail, n 1 = 12 d. of f. = 2.68 Test statistic: t = I Conclusion: The test statistic the critical value H0 and conclude that the mean mark