Shapiro-Wilks Test
Shapiro-Wilks Test of Normality
Fewer than 50 Measurements
Other Normality Tests:
Description:
The Shapiro-Wilks method tests normal distribution of the data. The 1992 guidance document recommends this as the preferred test for normality in data sets with fewer than 50 measurements.
In ChemStatimplementation, the Shapiro-Wilks test can test the normality of data for any parameter for a selected monitoring location, for all background monitoring locations, for all compliance monitoring locations, and for all monitoring locations. Select the monitoring location group from the right-click menu. The selected group should contain fewer than 50 measurement values.
The Shapiro-Wilks test can also be used to test for normality of the residuals. From the normality sub-menu on the right-click menu, select Residuals to test the residuals. Select Data to test the actual parameter concentrations for normality.
Use:
To test for normality in data sets with fewer than 50 measurements. The test can be performed on the selected monitoring location, all compliance monitoring locations, all background monitoring locations, or all monitoring locations.
Remarks:
This test uses values determined from tables based on the number of measurements. Because the tables accommodate only up to 50 measurements, this test can not be used for data sets with greater than 50 measurements.