Clark heter is an industrial engineer at lyons products. he would like to determine whether there are more units produced on the night shift than on the day shift. the mean number of units produced by a sample of 54 day-shift workers was 331. the mean number of units produced by a sample of 60 night-shift workers was 338. assume the population standard deviation of the number of units produced on the day shift is 19 and 26 on the night shift. at the .01 significance level, is the number of units produced on the night shift larger?