An industrial engineer would like to determine whether there are more units produced on the afternoon shift than on the morning shift. A sample of 50 morning-shift workers showed that the mean number of units produced was 345, with a standard deviation of 21. A sample of 60 afternoon-shift workers showed the mean number of units produced was 351, with a standard deviation of 28 units. At the .05 significance level we will test if the mean number of units produced on the afternoon-shift is larger. Is this a one sample test or a two sample test?