One-way ANOVA (cont...)
My p-value is greater than 0.05, what do I do now?
Report the result of the one-way ANOVA (e.g., "There were no statistically significant differences between group means as determined by one-way ANOVA (F(2,27) = 1.397, p = .15)"). Not achieving a statistically significant result does not mean you should not report group means ± standard deviation also. However, running a post hoc test is usually not warranted and should not be carried out.
My p-value is less than 0.05, what do I do now?
Firstly, you need to report your results as highlighted in the "How do I report the results of a one-way ANOVA?" section on the previous page. You then need to follow-up the one-way ANOVA by running a post hoc test.
Homogeneity of variances was violated. How do I continue?
You need to perform the same procedures as in the above three sections, but add into your results section that this assumption was violated and you needed to run a Welch F test.
What are post hoc tests?
Recall from earlier that the ANOVA test tells you whether you have an overall difference between your groups, but it does not tell you which specific groups differed – post hoc tests do. Because post hoc tests are run to confirm where the differences occurred between groups, they should only be run when you have a shown an overall statistically significant difference in group means (i.e., a statistically significant one-way ANOVA result). Post hoc tests attempt to control the experimentwise error rate (usually alpha = 0.05) in the same manner that the one-way ANOVA is used instead of multiple t-tests. Post hoc tests are termed a posteriori tests; that is, performed after the event (the event in this case being a study).