Before
creating a new command file for the model given above, the
relevant MDM file on which the analysis is to be based must
be selected. This is done by selecting the option Create
a new model using an existing MDM file from the File
menu.
The user
is then prompted for the name of the MDM file.
Click Open
after selecting the MDM file. The following information is
displayed in the main WHLM window. On the left of the main
window, the level1 variables for which information is available
in the MDM file are given in a list box.
As a first
step, the variable MATHACH, representing a student's math
achievement, is selected as the outcome variable. By clicking
on the variable name, a selection menu is displayed, with
the only active option Outcome variable, as shown below:
Once the
outcome variable has been selected, the following basic model
is displayed in the WHLM window.
As the
math achievement on level 1 of the model is to be modeled
in terms of the student's social class, the variable SES is
now added to the level1 model. Clicking on the variable name
SES leads to the display of a popup menu, on which a number
of options are available.
Select
the option add variable group centered, indicating
that the group mean is to be used as point of reference. Once
this option has been selected, the additional variable is
displayed in the WHLM window in a bold font, indicating the
fact that the particular variable is group mean centered.
The predictor now appears in the equation window and each
regression coefficient associated with it has become an outcome
in the level2 model.
Note that
in HLM 6 only the intercept coefficient,, is assumed to be vary randomly over level2
units. The slope of the level1 predictor(s) is assumed fixed.
This concludes
the specification of the level1 model. In the level2 model,
both the intercept and SES slope are to be modeled as dependent
on the school's mean social class (MEANSES) and school sector
(SECTOR).
Start by
clicking on the Level2 button on the left of the window.
This leads to the display of the variables on which information
at this level (>> Level2 <<) is available in
the MDM file. Select the equation for by clicking on it, as predictors will be added
to this equation first. The procedure to add variables to
the equation for is similar and is initiated by clicking on the equation for
before adding variables.
Select
variables to be added to the level2 equations as before.
Click on a variable name to display a popup menu. Both the
variables MEANSES and SECTOR are added uncentered to
the model:
Repeat
the variable selection procedure on the equation for so that the variables
MEANSES and SECTOR are also added uncentered to the
equation.
The at the end of the equation is grayed out. The error
term can be toggled by clicking on
the error term, .
The model
discussed in the introduction is obtained:
HLM 6 can
also display the model in other two alternative forms. The
mixed model is obtained by clicking the Mixed button
on the bottom right of the main window:
The model
with complete subscripts is obtained by the following steps:
Select
the Preferences option from the File menu to
bring out the Preferences dialog box as shown below.
Check the
box for the request Use level subscripts. Click OK
button.
The model
with complete subscripts is displayed as follows. Note that
both the “standard” model and the mixed model now
have all subscripts displayed.
Before
running the analysis, save the newly constructed command file.
This is done by selecting the Save As option from the
File menu and assigning a filename when prompted to
do so.
After saving
the command file, clicking the Run Analysis option
at the top of the main window initiates the analysis. A screen
showing details of the iterative procedure is shown. Note
that the information on the screen is also given as part of
the WHLM output file.
