Chapter 7: Analysing the Data Part IV : Analysis of Variance

One-Way Between Groups ANOVA

One-way between groups analysis of variance (ANOVA) is the extension of the between groups t-test to the situation in which more than two groups are compared simultaneously. Both the between groups t-test and the repeated measures t-test extend to ANOVA designs and analysis. It is also possible to combine between groups comparisons and repeated measures comparisons within the one design. In this chapter, however, we consider between groups designs only. Repeated measures designs are not available on SPSS Student Version and will be left until PSYC 302 Advanced Statistics. ANOVA designs are very widely used and are very flexible which is why we are focussing on them so much.

Terminology

Note the use of 'one-way' in the title. This indicates that only one Independent Variable is being considered (also sometimes called one factor). When we come to consider two IVs (or factors) at the one time we get a two-way ANOVA and a factorial design.

A factor in a one-way ANOVA has two or more levels. Normally there only two to five levels for the IV, but theoretically it is unlimited. Note that Howell (Chapter 11) describes this design and analysis technique as a "Simple" Analysis of Variance! T-tests can be done using the one-way procedure (i.e., with two levels); in which case, the F you get will be equal to t2.