Let’s read in an example dataset, crf24, adapted from Kirk (1968, First Edition).
get file 'c:https://stats.idre.ucla.edu/wp-content/uploads/2016/02/crf24.sav'.
First, let’s look at a table of the cells means to see what variables are in the data set. A and B may be considered independent variables, and y the dependent variable.
MEANS TABLES=y by a by b.
Case Processing Summary Cases Included Excluded Total N Percent N Percent N Percent Y * A * B 32 100.0% 0 .0% 32 100.0%
Report
YA B Mean N Std. Deviation 1 1 3.75 4 1.500 2 4.00 4 .816 3 7.00 4 .816 4 8.00 4 .816 Total 5.69 16 2.120 2 1 1.75 4 .500 2 3.00 4 .816 3 5.50 4 .577 4 10.00 4 .816 Total 5.06 16 3.316 Total 1 2.75 8 1.488 2 3.50 8 .926 3 6.25 8 1.035 4 9.00 8 1.309 Total 5.38 32 2.756
Now, let’s plot the cell means.
graph /line(multiple) mean(y) by b by a.
If you would like the means marked by a symbol, double click on the graph, select "format", select "interpolation", and select "straight". Make sure that the "display markers" box is checked. Click on "apply", then "close" and then close the chart editor. If you would like to change the markers, double click on the graph (again), select select "format", then "marker", and then select the marker and the size that you would like. If you would like to have different markers for the different groups, double click on the graph, double click on the legend on the right that labels the groups, and select (i.e., single click on) the group whose symbol (i.e., marker) you would like to change. Next, select "format", "marker", and then select the marker and the size that you would like. Click on "apply", then "close" and then close the chart editor.
graph /line(multiple) mean(y) by b by a.
You can also obtain this graph by using the glm command. Note that the first variable listed in the parentheses after profile will appear on the x-axis. The second variable listed will indicate the "grouping" variable.
glm y by a b /plot = profile(b*a).
Between-Subjects Factors N A 1 16 2 16 B 1 8 2 8 3 8 4 8
Tests of Between-Subjects Effects
Dependent Variable: YSource Type III Sum of Squares df Mean Square F Sig. Corrected Model 217.000(a) 7 31.000 40.216 .000 Intercept 924.500 1 924.500 1199.351 .000 A 3.125 1 3.125 4.054 .055 B 194.500 3 64.833 84.108 .000 A * B 19.375 3 6.458 8.378 .001 Error 18.500 24 .771 Total 1160.000 32 Corrected Total 235.500 31 a R Squared = .921 (Adjusted R Squared = .899)
