Calculate Z-score

A z-score refers to the number of standard deviations each data value is from the mean, with a z-score of zero indicating the exact mean. Z-scores are useful for analyzing numbers in the context of the rest of the field.

To learn more about z-scores, see What is a z-score? What is a p-value?.

Example

A GIS analyst for a nongovernmental organization is analyzing a disease outbreak. Calculate Z-score can be used to determine the areas in which the outbreak is concentrated.

Use the Calculate Z-score capability

Use the following steps to run the Calculate Z-score analysis capability:

1. Create a map, chart, or table using the dataset with which you want to calculate the z-score.
2. Click the Action button .
3. Do one of the following:
   • If your card is a chart or table, click How is it distributed? in the Analytics pane.
   • If your card is a map, click the Find answers tab and click How is it distributed?.
4. Click Calculate Z-score.
5. For Choose a layer, select the dataset with which you want to calculate the z-score.
6. For Choose number field, choose the field you want to use to calculate the z-score. The field must be a number or rate/ratio.
7. Expand Additional options and enter values for Mean and Standard Deviation, if necessary. If no values are entered, the mean and standard deviation will be calculated for you.
8. For Name the result field, enter a name for the new field.
9. Click Run.

Usage notes

Calculate Z-score can be found using the Action button under How is it distributed? on the Find answers tab. The input layer can be a point, a line, or an area layer.

A number field must be chosen as the field to calculate the z-score. The number field will be used in the equation (number-average)/standard_deviation.

Optionally, you can enter mean and standard deviation values. If you don't enter values, the mean and standard deviation will be calculated for you.

Calculate Z-score adds a new number field to the input layer. The field name is automatically populated in the Calculate Z-score pane, but you can change it before running the calculation.