Answer to first part 1: First you obtain number of intervals you would like to have by getting the square root of the total number of observations. In this case, square root of 14 = 3.74; round up and use 4.0. Answer to Second part: 2: The interval width is then obtained by dividing the range by the number of intervals. For this case, interval width = (42-9)/4 = 8.25. This can be rounded up to the convenient evenfigure of 10.0.
