I would really appreciate recommendations for good examples of planned contrasts following both significant and non-significant ANOVAs. I am especially interested in how these are expressed in APA 7th guidelines.
In the context of one-way ANOVA, the term planned comparison is used when:
You focus in on a few scientifically sensible comparisons rather than every possible comparison.
The choice of which comparisons to make was part of the experimental design.
You did not succumb to the temptation to do more comparisons after looking at the data.
It is important to distinguish between comparisons that are preplanned and those that are not (post hoc). It is not a planned comparison if you first look at the data, and based on that peek decide to make only two comparisons. In that case, you implicitly compared all the groups.
The advantage of planned comparisons
By making only a limited number of comparisons, you increase the statistical power of each comparison.
Choices when doing planned comparisons. A. Correct for multiple comparisons?
There are two approaches to analyzing planned comparisons:
Use the Bonferroni correction for multiple comparisons, but only correct for the number of comparisons that were planned. Don't count other possible comparisons that were not planned, and so not performed. In this case, the significance level (often set to 5%) applies to the family of comparisons, rather than to each individual comparison.
Set the significance level (or the meaning of the confidence interval) for each individual comparison. The 5% traditional significance level applies to each individual comparisons, rather than the whole family of comparisons as it does for multiple comparisons.
- Badges
- Science method
- Similar topics
- Mathematics
- Statistics
- Statistical Modeling
- Analyses of Variance
- ANOVA