To compare two programs for training industrial workers to perform a skilled job, 20 workers are included in an experiment. Of these, 10 are selected at random and trained by method 1; the remaining 10 are trained by method 2. After completion of training, all the workers are subjected to a time-and-motion test that records the speed of performance of a skilled job. The following time, as measured in minutes, is obtained.

Method 1: 15 20 11 23 16 21 18 16 27 24

Method 2: 23 31 13 19 23 17 28 26 25 28

Test the hypothesis that the mean job time is significantly less after training with method 1 than after training with method 2. Use a signficance level of α = 0.05.