(a) A wavy line across the bottom of the grid, (bl A straight line waved at each end.

STANDARDS FOR TIME SERIES CHARTS

RANGE AND SPACING OF AMOUNT SCALE

Principl*!

1. Since the omount scole has a controlling effect on the movement oi the curves it is highly important that a scale be selected which will result in a true picture of the facts.

2. The amount scale should be divided in a manner that will facilitate accurote reading of the curve values.

Procedures

1. FULL RANGE DESII^ABLE. Generally the amount scale should begin at zero. It should extend continuously to a point somewhat beyond the greatest value, to avoid crowding the grid. In cases of marked upward trends, curves generally should not point obove the upper right-hond corner of the grid.

2. AVOID WASTE SPACE Unnecessary extension of the scale range should be avoided if blank space which serves no useful purpose is thus added.

Noie Eoendino 't<e scole range reduces the fluciuotion and separation of Curves When this is desirable it mov be belter accomplished by reducing the Koie dimensions i( the resulting chorl con still be made ol the desired proportions.

3. "FREAK" VALUES. Where a series contains a few widely divergent points lunless they ore really significant) it is often better not to attempt to select a scale that will include them all. Inclusion of these points will tend to depress the fluctuations of the rest of the curve.

4. DIVISION OF SCALE. It is desirable to select a scale range that is divisible into convenient scale intervals.