A notched box and whisker diagram can be created displaying a confidence interval about the median value in Grapher using the steps below:
- Click the Home | New Graph | Statistical | Notched Vertical Box Plot () command or the Home | New Graph | Statistical | Notched Horizontal Box Plot () command.
- In the Open Worksheet dialog, select the data file and click Open. The default notched box-whisker plot is created.
- Click on the box plot layer in the Object Manager to select the box plot (underneath Graph 1).
- In Grapher 13 and previous this will be named Box-Whisker Plot 1.
- In the Property Manager, click on the Plot tab.
- If desired, you can edit the notch Factor.
- The notch Factor is the value multiplied by the standard deviation of the median. The default notch Factor of 1.7 approximately shows 95% confidence in the median.
- If you would like to increase the degree of confidence in the median values, increase the notch Factor. For most cases, a value of 1.96 would show approximately 99% confidence in the median. A smaller value would result in a more conservative a test of the confidence.
- Appropriate values range between approximately 1.3 and 1.96. To edit the value, highlight the existing value and type the desired value. Press ENTER on the keyboard to make the change.
A Vertical and Horizontal Notched Box-Whisker Plot with
the notch Factor set to 1.7.
Updated September 17, 2018