Page:Graphic methods for presenting facts (1914).djvu/210

 chart shows that the department to which curve "G" relates handles a larger percentage of the total number of packages and produces a larger percentage of the revenue than the department to which curve "E" relates. If this chart had been plotted on a "less than" basis instead of on a "more than" basis, the position of these two curves giving detailed information for the main curve "F" would be exactly reversed, with curve "E" appearing above the heavy line "F" and curve "G" appearing below the heavy line.

It is perhaps well to point out an error in drafting which occurred on Fig. 158. The information most needed relates to orders containing less than three hundred packages each. It was, however, desired to show on the chart that none of the orders contained more than five hundred packages, and the right-hand portion of the chart is accordingly shown with a break, indicating that a section has been omitted. As a general rule, when making a break in a drawing in this manner, the two portions on either side of the break are made exactly as though a piece of paper had been torn out of the middle of a drawing made large enough to include the whole chart. Fig. 158 is incorrectly made in that the curve lines to the right of the figure 300 on the horizontal scale have been drawn pointing down toward the right-hand corner of the chart where they show at the left of the break. These lines would not appear this way if a piece of paper had been torn out of a large-size chart. The curve lines should have continued up to the break in the drawing more nearly on the slope seen in the left-hand portion of the chart. The lines for curves "G", "F" and "E" would, if correctly made, show much less slope also at the right of the break where they lead down to the lower corner of the chart. This error is mentioned here simply that the reader may have some guidance if he finds it necessary to make charts including a break, similar to that shown in Fig. 158.

It is customary in cost-keeping work to make costs which show only an average of the cost per unit, on an average for all orders completed during a period of time, say one month or one year. Though this method of averaging all orders together without respect to the size of the order is sufficiently accurate for many purposes, there are times when such a method may gravely mislead an executive. It is almost invariably true that small orders cost more per unit of output than orders of large size. A man who makes a selling price for his work on the average cost of small orders and large orders combined may be