Weight of Rails per Yard in the Main Line Track of the Seaboard Air Line Railway as Published in the Annual Report to Stockholders for the Fiscal Year Ending June 30,

When using the left-hand scale the chart is read on a "more than" basis as if the words "more than" had been used with the horizontal scale as seen in Fig. 158. If the right- , , . 1 1 1 ■ ■ 1 hand scale is selected the words "less than" are used

this book are plotted on a

"more than" basis, so that curves involving the larger quantities or percentages may appear on the chart above those cumulative frequency curves for smaller quantities or percentages.

Fig. 152 and Fig. 153 show the application of the cumulative frequency curve to commercial problems. The full explanation of these

GRAPHIC METHODS

two charts cannot be gone into here, but the reader can see for himself the use of the cumulative frequency curve in studying different problems in the telephone business. In Fig. 152 the curves show the time required to answer calls in different cities, while Fig. 153 shows a comparison of answering times in different classes of service. Notice that in each of these two charts it seems that two seconds is about the minimum which can be expected in answering telephone calls with the existing types of equipment. Fig. 153 certainly gives in excellent manner the comparison between the answering times for different classes of service. It would be very difficult to convey the complex information contained