13.1 The air pressure (in psi) at a point near the end of an air-supply line is monitored at 15-min intervals over an 8-h period. The readings are listed in the four columns that follow: Column 1 Column 2 Column 3 Column 4 113 105 100 97 107 101 96 100 109 98 93 103 97 123 87 105 95 118 81 110 92 112 85 113 103 103 91 120 117 101 94 128 List the pressure readings in order of increasing magnitude. Rearrange the data in five-group intervals to obtain a frequency distribution. Show both the relative frequency and the cumulative frequency in this tabular rearrangement. Select the median pressure reading from the data. 13.2 Construct a histogram for the data listed in Exercise 13.1. Superimpose a plot of the relative frequency on the histogram. 13.3 Find the mode for the individual data then find the mode using the constructed histogram.