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Two additional visual cues, error bars and trendlines, can help your readers understand your data more quickly. Error bars show the error margin built into each data marker, and trendlines use an analysis of existing data to predict future behavior.
You can create error bars for the data series in your 2-D area, bar, column, and line charts, as well as bubble and xy (scatter) charts. To add error bars to your chart, follow these steps:
Figure 19-16. Use the Format Data Series dialog box to add error bars that show a margin for error in which the result could be a bit higher or lower than what's shown in your chart.
Trendlines are helpful when you want to use your chart as a basis for either looking ahead to future possibilities or seeing trends in the past. You can add trendlines to area, bar, bubble, column, line, stock, and xy (scatter) charts. When you've created one of these chart types, adding a trendline is simple. Here are the steps:
Figure 19-17. In the Add Trendline dialog box, select the formula you want Microsoft Graph to use to plot your projections.
Tip - Find out more about trendlines
If you want to understand more about the equations the trend types use to calculate trends in your data, click the What's This? button in the Add Trendline dialog box and click the trend type you want to see. A ScreenTip gives you more information about the trend type you've selected.
Figure 19-18. A trendline in your chart can show a general direction for your data and helps readers understand at a glance what the significant changes in your data might be.