A contrasting method of showing all curves plotted separately but from the same zero line. Universal co-ordinate paper for convenience in curve plotting. Total curves with component areas so that any point on a curve totals 100 per cent for the height of the areas beneath.

Chapter IX. Cumulative or Mass Curves 149

Factory production schedules and actual outputs plotted on a cumulative basis. Curves for income and expense on a cumulative basis. Various uses for cumulative curves. Cumulative curves with lines drawn to show rate

CONTENTS XI

of change. A grand total cumulative curve plotted from several other cumulative curves. Cumulative curves for the determination of storage requirements for water supplies.

Chapter X. Frequency Curves. Correlation 164

The arrangement of objects so that their position shows a crude frequency curve. Vertical bars to represent frequency. Frequency curves. The "mode." Frequency curves much easier to interpret than charts using bars or areas. Cumulative frequency curves. The use of cumulative frequency curves for business problems. Cumulative frequency curves preferably plotted on a "more than" basis instead of on a "less than" basis. Necessity for making the independent variable the horizontal scale. Wage comparisons for industrial work. Studies of the percentage of clerical work and percentage of revenue from orders of various sizes. Pin boards to record costs of doing work on orders of different size. Theoretical curves for percentage of clerical work and percentage of revenue from orders of different size. The Lorenz curve. Correlation curves. "Shotgun" diagrams. Plotting curves to represent numerous points. Shaded areas to represent numerous dots. Correlation charts for two independent variables. Isometrically ruled paper for chart work.