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GRAPHIC PRESENTATION

RELATION OF TIME SCALE TO AMOUNT SCALE

1. The relofion between the time scale and the amount scale has a determining influence on the movement of time-series curves.

Note: The movement of o curve ij here understood to meon the o'opf^ic effect of the progressive chonges in the quantity considered The trend is the graphic effect of the overoil changes in the quontity considered

2. Selection of both scales should be made to convey the correct impression of the trend and movement of the series.

3. Manipulating the scales so as to picture a movement contrary to the facts is never justiPied.

True picture

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Distortion fMultino from oinitslon of zero value

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Methods of Indicating omluion of zero volue

•00 1935 1935

Effect of altering grid proportions

INCLUSION OF PRINCIPAL POINT OF REFERENCE

Principle

1. The amount scale should normally include the zero value or other principal point of reference. Departure from this rule should never be made except where there is a special reason for so doing.

Procedures

1. WHEN NECESSARY. The zero line or other base of comparison should never be omitted when the interest is in relative amount of change between points on the same curve.

2. WHEN NOT NECESSARY. When the interest of the reader is in the absolute amount of change rather than in the relative amount of change, it may be safe to omit the principal point of reference and the accompanying horizontal line.