The following data represents the number of cigarettes smoked per day for a sample of 18 teenagers each of whom identifies as a smoker:

26, 15, 21, 26 ,9 ,31 ,20 ,30 ,21, 0, 19, 25, 16, 32, 14, 27, 28, 18

a) Sketch a box-and-whisker plot on graph paper. Indicate and outliers.

b) What is the advantage of representing the data using a box-and-whisker plot as compared to a stem-and-leaf display?