Planned comparisons

Both the Means procedure and one-way confirmed that there is a significant difference in education across the nine US regions. Often, however, there is a need to test whether two specific group's, out of the set of group's, differ significantly. Contrasts can be used to perform this test.

The Contrast dialog (refer to the following figure) can be used to define a variety of contrasts to test for the Means, including polynomial and linear. Here, a simple contrast is defined by associating a contrast value with each of the six values of the RES16 field. Setting the values at one through four to zero indicates they are not part of this comparison. The fifth value, big-city suburb, is set to 1, and the sixth value, big city, ...

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