It is the convention that positive values are measured upword from the horizontal oxis and to the right of the verticol axis and negative values ore measured downward from the horizonlol axis and to the left of the vertical axis.

4. In o time-series chart the vertical or Y axis measures amount, ond the horizontal or X oxis meosures time.

5. Time values In o time-series chart ore usuoily represented as positive and move from left to right on the horizontal or time scale.

6. Every plotted point in o time-series chart has two values: An amount volue meosured on the verticol oxis ond o time value measured on the horizontal axis.

7. The horizontal oxis, zero line or other line of reference, should be accentuated so os to indicate that it is the bose for comparison of volues. There is no such bose of comporison for the time scale in a lime-series chart, however, there being no beginning or end of time.

8. In o time-series chart the plotted points ore generolly joined consecutively by straight lines to form o continuous line movement which is conventionally spoken of as o curve. The points of volue con be indicated by means of other grophic forms such os columns or surfoces, but the fundomentol principle is the some.

9. The values on the omount scale should be continuous,- and points on the scale with their corresponding horizontol rulings should reflect the actual intervals on the scale.

10. Time should be regarded os continuous with vertical rulings used to indicate only certain intervals of time. Equol intervals of time should be indicoted by equal space intervols on the scale.