One-Way ANOVA


As in the independent t-test datasheet, the data must be coded with a group variable. The data that will be used for the first part of this section is from Table 11.2, of Howell. There are 5 groups of 10 observations each - resulting in a total of 50 observations. The group variable will be coded from 1 to 5, for each group. Take a look at the following to get an idea of the coding.


GroupsScores
19
18
16
......
17
27
29
26
... ...
......
......
510
519
......
511

The coding scheme uniquely identifies the origin of each observation.

To complete the analysis,

The analysis that was just performed provides minimal details with regard to the data. If you take a look at the controlling dialog box, you will find 3 additional buttons on the bottom half - [Contrasts...], [Post Hoc..], and [Options...].



Selecting [Options...] you will find,



If Descriptive is enabled, then the descriptive statistics for each condition will be generated. Making Homogeneity-of-variance active forces a Levene's test on the data. The statistics from both of these analyses will be reproduced in the output window.

Selecting [Post Hoc] will launch the following dialog box,



One can active one or multiple post hoc tests to be performed. The results will then be placed in the output window. For example, performing a R-E-G-W F statistic on the current data would produce the following,



Finally, one can use the [Contrasts...] option to specify linear and/or orthogonal sets of contrasts. One can also perform trend analysis via this option. For example, we may wish to contrast the third condition with the fifth,



For each contrast, the coefficients must be entered individually, and in order. Once can also enter multiple contrasts, by using the [Next] present in the dialog box. The result for the example contrast would look like the following,





Further, one can use the Polynomial option to test whether a specific trend in the data exists.

Factorial designs will be covered in the next section.