Example: Specifying a Regression Model that Will Evaluate Differences Across Groups

In this example, we will specify a regression model that will evaluate differences across groups. For this example, the groups represent two different manufacturing plants (plant locations A and B, variable v1) at two different time periods (week 1 and week 2, variable v2) and variable v3 is the dependent variable (an efficiency measurement).

1. In the Estimated Function or Estimated Function and Loss Function dialog, first specify the desired regression model in the general form for models:

v3 = b0 + b1*v1 + b3*exp(b2*v2)

2. If you selected User-specified Regression, Custom Loss Function from the Startup Panel, you also need to specify the desired loss function [option User-specified Regression, Least Squares will automatically use the least squares loss function in conjunction with the efficient Levenberg-Marquardt Algorithm (Nonlinear Least Squares)]. For example:

L = (obs - pred)2

the standard least squares loss function (this is the default entry in the loss function field).

3. Once you have entered the desired model and loss function, click OK to exit the dialog and proceed with the analysis. STATISTICA will automatically check the syntax of the expressions for errors and notify you if there are any.

See also: General syntax conventions: Regression equations and Example: Using logical expressions to estimate regression parameters.