XL97: Chart Polynomial Trendline Formula Is Inaccurate

• Microsoft Excel 97 for Windows

SYMPTOMS

The equation displayed for a polynomial trendline on an xy (scatter) chart is incorrect. When you manually substitute values for the x variable, Microsoft Excel then plots the trendline incorrectly.

CAUSE

Microsoft Excel 97 plots polynomial trendlines correctly; however, the equation that is displayed may give incorrect results when you manually type x values. For appearance, each x value is rounded in the number of significant digits that are displayed in the chart. This allows the equation to occupy less space in the chart area. However, the accuracy of the chart is significantly reduced, which can cause a trend to appear to be incorrect.

WORKAROUND

To work around this behavior, increase the digits in the trendline equation by increasing the number of decimal places that are displayed. To do this, use the following steps:

1. In the chart, select the trendline equation.

2. On the Format menu, click Selected Data Labels.

3. Click the Number tab, and click Number in the Category List.

4. Increase the number of decimal places to 8.

5. Click OK.

STATUS

This behavior is by design of Microsoft Excel 97 for Windows.