To compare two different keyboard layouts on a pocket calculator, a company divided 21 staff volunteers randomly into a group of 10 (A) and a group of 11 (B). Each group was asked to carry out the...

To compare two different keyboard layouts on a pocket calculator, a company divided 21 staff volunteers randomly into a group of 10 (A) and a group of 11 (B). Each group was asked to carry out the same set of calculations, group A using the first type of keyboard, and group B the second. Individuals were assessed on the total time (in minutes) taken to complete the calculations. These times are given in the table below. Use an appropriate test to determine whether one layout is preferable to another.