Identify a Source Variable

Before running the Weight Estimation procedure, you need to determine a variable that is associated with the source of heteroscedasticity. Based upon the experience of the developers, you suspect that the size of the mall may serve as such a variable.

  1. To determine whether this is the case, from the menus choose:

    Graphs > Chart Builder...

    Figure 1. Chart Builder
    Chart Builder
  2. Select the Scatter/Dot gallery and choose Simple Scatter.
  3. Select Standardized Residual as the y variable and Square Footage as the x variable.
  4. Click OK.
Figure 2. Scatterplot of Residuals by Square Footage
Scatterplot of Residuals by Square Footage

The pattern that was evident in the residuals vs. predicted values plot can be seen here. Square Footage should be acceptable as a source variable for generating weights to correct for the heteroscedasticity.

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