Shared Statistical Concepts
Continuous-by-class effects generate the same design columns as continuous-nesting-class effects. Table 4.13 shows the construction of the X*A effect. The two columns for this effect are the same as the columns for the X(A) effect in Table 4.12.
Table 4.13: Example of Continuous-by-Class Effects
|
Data |
I |
X |
|
|
|||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
|
|
X |
A1 |
A2 |
X*A1 |
X*A2 |
||||
|
21 |
1 |
1 |
21 |
1 |
0 |
21 |
0 |
||||
|
24 |
1 |
1 |
24 |
1 |
0 |
24 |
0 |
||||
|
22 |
1 |
1 |
22 |
1 |
0 |
22 |
0 |
||||
|
28 |
2 |
1 |
28 |
0 |
1 |
0 |
28 |
||||
|
19 |
2 |
1 |
19 |
0 |
1 |
0 |
19 |
||||
|
23 |
2 |
1 |
23 |
0 |
1 |
0 |
23 |
||||
You can use continuous-by-class effects together with pure continuous effects to test for homogeneity of slopes.