1.47 A supervisor of a plant kept records of the time (in seconds) that employees needed to complete a particular task. The data are summarized as follows:

Time 30 6 40 40 6 50 50 6 60 60 6 80 80 6 100 100 6 120 Number 12 13 22 34 24 22

a. Graph the data with a histogram.

b. Discuss possible errors.