Page:Graphic methods for presenting facts (1914).djvu/110

 page is held up toward a light. The curve for operator No. 1 then appears below the curve for operator No. 2 and the chart shows correctly the relative merits of the two operators. Fig. 86 is a redrawing of the data shown in Fig. 85. Here the curves for the two operators appear in their correct relative position, and it is seen at once that operator No. 1 is the more rapid worker, since he uses less time. With the independent variable made the horizontal scale, a chart can be interpreted quickly. If the dependent variable is used as the horizontal scale the reader is likely to draw a conclusion the reverse of that the chart was intended to show.

Adapted from System

Fig. 85. Record of a Detailed Time-Study of Two Operators Labeling Packages

We are here studying the time for different operations. The names of the operations constitute the independent variable while time is the dependent variable. The chart reverses the proper arrangement of scales and causes the curve for operator No. 1 to appear improperly above the curve for operator No. 2. Compare Fig. 86

Fig. 87 shows the data of Fig. 85 and Fig. 86 redrawn in the form of horizontal bars such as were seen in Chapter I and Chapter II. The relative times for the various operations are shown much more clearly by the horizontal bars than by the curves used in Fig. 85 and Fig. 86. The time in seconds required for each operation is given by detailed dimension lines above each section in the horizontal bar, and the comparative total time of the two different men can also be grasped instantly. The total time in seconds for the whole series of operations is shown by an over-all dimension line above each of the bars, and the reader, if he wishes, may make an accurate comparison between operator No. 1 and operator No. 2 by using a numerical ratio. A chart of this kind can be very quickly made for ordinary office purposes if the horizontal bars are drawn on co-ordinate paper