Battery Lifetime. In the article “Comparing the lifetime of two brands of batteries” (Journal of Statistical Education, Vol. 21, No. 1, pp. 1–19) by P. Dunn, two brands of AA alkaline batteries were compared. The following table gives the number of pulses required for a sample of 18 Energizer and Ultracell batteries to reach a voltage level of 1.3.

   

37	57	37	46	56	44
47	54	58	56	38	57
57	34	57	60	54	40

a. Construct a stem-and-leaf diagram for these data with one line per stem.

b. Construct a stem-and-leaf diagram with two lines per stem.

c. Which stem-and-leaf diagram do you find more useful? Why?