Line charts contain more data in a compact space than do the other types of charts. They should be used when a large number of points are to be plotted, when several series are being compared, or when emphasis is on movement and not on actual amounts. Actual numbers or rates can be charted to provide a running total or average. Multiple lines can be plotted to provide comparison and trends of two data values over the same time period. However, it is not recommended to plot more than four or five lines on a chart, especially if the different data points for the lines are close in value.
Excessive range minimizes differences in the data and wastes space.
Too small of a range may result in an exaggerated picture of the differences. PC software graphics packages automatically assign a scale. However, if you do not like the range assigned by the software, there are usually options that allow you to change the range. Quality Assurance Copyright 2001 Commonwealth of Pennsylvania. All Rights Reserved.