Error graphs display not only a Y-value for each X-value, but a range of Y-values for a given X-Value. Error graphs are typically used to display the variation of each data point around its central value. For each X value in an Error graph, there is an associated Y value and an ``error range'' value that represents the deviation from the Y value.
Just as with line and bar charts, Error graphs can show multiple sets of data. You can use the Data Sets dialog box to change the horizontal tick marks into boxes, circles, etc. You can also use the Skew Data button in the General graph dialog to offset the data sets from each other. This helps in discriminating the data points of one data set from another. The points in each data set can also be connected with line segments or splines. You have the same flexibility in determining the look of the Error graph as you do with Line and Scatter graphs.
Figure 12.16: Error Graph