When you plot statistical or experimental data, it’s often helpful to indicate the confidence level of your data. The Excel error-bar feature makes this easy. To add error bars to a data series in an area, bar, column, line, or X Y (scatter) chart, select the series, click the Layout tab, and then click Error Bars (in the Analysis group). As with trendlines, unless your intention is to remove existing error bars (in which case, click None), there’s little point in resting your pointer on the options that drop down from the ribbon; instead, click More Error Bars Options to get to the dialog box shown in Figure 21-23. Here you can tailor your error bars and specify the range of values you want them to encompass.

Figure 21-23. You can customize error bars for direction, style, and amount.