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One-way ANOVA

Command: Math -> ANOVA -> One Factor...

The command Math/ANOVA/One Factor... performs a one-way ANOVA. You have to select two columns, one containing the treatments, the other containing the dependent variable. When both columns have been selected the results of the ANOVA is displayed (SS stands for sum of squared residuals, DF for degrees of freedoms, and MSS for the variances).

In order to test whether at least one mean of the treatments differs from the others, you have to compare the calculated F-value to the critical F-value. The level of significance can be set at the lower right of the window.

The prerequisite of equal variances can be checked by Levene's test. The null hypothesis of equal variances has to be rejected if the F value exceeds the critical limit.

Hint 1: The dependent variable has to contain data which are at the interval or ratio level of measurement, the treatments may be categorial, as well. Further, the treatments may be obtained from the class numbers.

Hinweis 2: It is a good idea to keep the power of Levene's test high in order to avoid high probabilities of making a type II error. Thus, the level of significance of Levene's test should be set to a high level (typically 10 or 20%).

Last Update: 2012-Jul-25