Information Technology Reference
In-Depth Information
Figure 16.26
Assigning the variables to axes of the scatterplot.
Select
Task Roles
in the navigation panel to the left of the window to
display the screen shown in Figure 16.26. Drag
math_dv
to the icon for
Vertical
and drag
verb_cov
to the icon for
Horizontal
.
Next, select
Plots
in the navigation panel to configure the scatterplot.
As shown in Figure 16.27, we have selected a black color for our output; you
can select other options if you wish. Click
Run
to perform the procedure.
The scatterplot is presented in Figure 16.28. It can be determined from
the plot that the covariate and the dependent variable are related to each
other in a linear manner. Therefore, the data appear to meet the linearity
of regression assumption.
16.11.2 HOMOGENEITY OF REGRESSION
To evaluate the assumption of homogeneity of regression in
SAS Enter-
prise Guide
, we configure the analysis similar to how we ran the ANOVA
described above. From the main menu select
Analyze
➜
ANOVA
➜
Lin-
earModels
. As shown in Figure 16.29, specify
math_dv
as the
Dependent
variable
and
group
as the
Classification variable
.Now,however,wewill
also specify
verb_cov
as the
Quantitative variable
(SAS makes explicit
the idea that it treats covariates as quantitative rather than categorical
variables).
Select
Model
in the navigation panel on the far left of the screen.
Highlight
verb_cov
and click the
Main
pushbutton in the middle of the
window. This action will place
verb_cov
in the
Effects
panel as shown
