An occupational therapist is investigating whether a new ergonomic keyboard design reduces the number of typing errors made during a standard 10-minute copy-typing task. She conducts an experiment using a sample of 12 professional typists. In the first session, the typists use a standard keyboard (Before) and record their errors. In the second session, after a week of practice, they use the ergonomic keyboard (After) and record the number of errors under identical typing conditions. The data for each participant is presented in the table below.

Number of typing errors during a 10-minute typing task