Page:Graphic methods for presenting facts (1914).djvu/166

 the fluctuations in the accidents of any one department over a long period of time.

As accidents never occur with any regularity, curves representing the actual number of accidents are likely to fluctuate a great deal. There was such variation in the different months for the number of accidents represented in Figs. 130 and 131 that it was almost impossible to draw any definite conclusion from curves for monthly data. The data for Fig. 130 and for Fig. 131 were plotted on the basis of giving, monthly, the average number of accidents in each department during the last twelve months for which records were available. Actual figures in tabulated form were used to show for immediate reference the number of accidents in any month. The curves on the twelve-months average basis were consulted to determine whether there was any great increase or decrease in any department.

New York Edison Company

Fig. 132. Nature of the Electrical Load Connected to the System of the New York Edison Company, 1893 to 1912

In the preceding illustrations 100 per cent was indicated by a straight line at the top of the chart. Here the line representing 100 per cent is a curve. Though the actual sizes of different components can be seen by this method, percentages can only be estimated from the widths of the areas. The scale for this type of chart must read in actual quantities rather than in percentages. On this wall exhibit the scale has been omitted entirely

In Fig. 132 the vertical scale was omitted, perhaps with the idea that the chart would thus appear more simple to the average indi