Q2. A study is conducted to assess the difference in performance during the first years of services between employees that stayed in a certain company during 15 years and those who left the company. The performance is measured by the company's annual performance appraisals which produce ratings on a 5 point scale, I for low performance and 5 for high performance. The data are summarized in the table. Use a = 0.05 to test the hypothesis. Stayers Leavers Sample size 174 355 Sample mean 3.51 3.24 Sample standard deviation 0.51 0.52