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What is the purpose of post hoc comparisons?
Post Hoc Tests. Post hoc (Latin, meaning “after this”) means to analyze the results of your experimental data. They are often based on a familywise error rate; the probability of at least one Type I error in a set (family) of comparisons.
What is the purpose of the post hoc multiple comparisons testing?
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).
How does a post hoc test control the error rate?
Post hoc tests control the experiment-wise error rate by reducing the statistical power of the comparisons. Here’s how that works and what it means for your study. To obtain the family error rate you specify, post hoc procedures must lower the significance level for all individual comparisons.
How are post hoc tests used in statology?
Post hoc tests allow us to control the family-wise error rate while performing multiple pairwise comparisons. The tradeoff of controlling the family-wise error rate is lower statistical power. We can reduce the effects of lower statistical power by making fewer pairwise comparisons.
Which is the most conservative post hoc test?
Another post hoc test we can perform is holm’s method. This is generally viewed as a more conservative test compared to Tukey’s Test. This test provides a grid of p-values for each pairwise comparison. For example, the p-value for the difference between the group A and group B mean is 0
What is the p value of a post hoc test?
To follow along with this example, download the CSV dataset: PostHocTests. The p-value of 0.004 indicates that we can reject the null hypothesis and conclude that the four means are not all equal. The Means table at the bottom displays the group means.