In the Fit Least Squares report, the Custom Test option enables you to test one or more custom hypotheses involving any model parameters. In the Custom Test window, you can specify one or more linear functions, or contrasts, of the model parameters.
The results include individual tests for each contrast and a joint test for all contrasts. The report for the individual contrasts gives the estimated value of the specified linear function of the parameters and its standard error. A t ratio, its p-value, and the associated sum of squares are also provided. Below the individual contrast results, the joint test for all contrasts gives the sum of squares, the numerator degrees of freedom, the F ratio, and its p-value.
Caution: These tests are conducted using residual error. If you have random effects in your model and if you use EMS instead of REML, then these tests might not be appropriate.
Note: If you are testing for effects that are involved in higher-order effects, consider using a test for least squares means, rather than a custom test. Least squares means are adjusted for other model effects. You can test least squares means contrasts under Effect Details.
The Custom Test specification window has the following components:
Editable text box
The space beneath the Custom Test title bar is an editable area for entering a test name.
Parameter
The model terms. To the right of the list of terms are columns of zeros corresponding to the corresponding parameters. Enter values in these cells to specify the linear functions for your tests.
The “=” sign
The last line in the Parameter list is labeled =. Enter a constant into this cell to complete the specification for each contrast.
Add Column
Adds columns of zeros so that you can jointly test several linear functions of the parameters.
Done
Click the Done button to perform the tests. The report changes to show the test statistic value, the standard error, and other statistics for each test column. The joint F test for all columns is given in a box at the bottom of the report.
The Custom Test red triangle menu contains the following options:
Power Analysis
Provides a power analysis for the joint test. This option is available only after the test has been conducted. See Parameter Power.
Remove
Removes the Custom Test report.
Note: Select Estimates > Custom Test repeatedly to conduct several joint custom tests.
See “Example of a Custom Test” for an example that illustrates the use of the specification window for three contrasts.