Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

Questions tagged [post-hoc]

"post-hoc" refers to analyses that are decided upon after the data has been collected, as opposed to "a priori".

"post-hoc" refers to analyses that are decided upon after the data has been collected, as opposed to "a priori". The more the data is examined post-hoc and the more statistical tests are run on it, this should be taken into account by multiple-testing procedures.

It is also a (outdated) concept of causality "post hoc ergo propter hoc" (meaning "after this, therefore because of this"). The idea is that if we always observe event $Y$ after event $X$, $X$ must have caused $Y$. This concept underlies for instance the Granger causality test. Nowadays this post hoc notion of causality is not accepted as actual causality.

702 questions
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What is the problem with post-hoc testing?

My statistic professor says so, all the books that I look at state it: post-hoc-testing is unscientific. You must derive a hypothesis from theory first, and then collect data and analyse it. But I really don't understand what the problem…
user14650
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Alternative to Tukey's HSD

If one has dataset with a single outlier such as the following graph taken from Vanni-Mercer et al. (2009), is there a statistical test that one can use that accounts for the single outlier rather than having to throw it out or declare significance…
Phillip Cloud
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Post hoc Scheffé test

My 1-way ANOVA test is not significant. Is it possible that a Scheffé test as a post hoc test be significant? If not, please say why not.
Bernard
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Is Tukey's Predicted Least Squares an actual test?

A letter in a recent (2011) article of Nature doi:10.1038/nature09817 refers in several places to a Fisher's predicted least-square difference test. A google search returns 102 hits for "predicted least square difference" and 3 for "predicted least…
russellpierce
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Bonferroni's t critical value

Post hoc tests, like Bonferroni, allow us to detect which of the groups is the different one after ANOVA. To use it, we calculate effectively what is like the independent t-test for each of the pairwise groups. This value is then compared to the $t$…
John Hon
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One tailed p-values for post-hoc tests

Is it okay to calculate one tailed p-values from post-hoc tests? I read this from a source but I just want to confirm it. "First, post hoc tests by their nature are two-tailed (you use them when you have made no specific hypotheses and you cannot…
Neal
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Is the Student–Newman–Keuls post-hoc test guaranteed to be stronger than the Tukey?

I am looking to compare two post-hoc analyses, one with the SNK test and the other with the Tukey. I have read that the SNK test is stronger but more likely to commit type 1 errors than the Tukey. Here is my question: if the Tukey test reports a…
Greg Markowsky
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Post-hoc Fisher test not significant after significant fisher test?

I am comparing proportions of different maturity stages (3 levels) between different treatments (4 levels). As I have some values less than 5 in some cells, I decided to use a Fisher exact test instead of a chi square. After doing the fisher test, I…
nathmar
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Is post hoc test needed for stepwise forward confounder/covariate model?

I did a GLMM (corrected for school and administration levels) and analysed the association between food environment and weight status. I corrected for several demographics and other urban variables. As I did a forward selection model with those…
katia00
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Multiple comparisons tests

Multiple comparisons tests, such as Dunnett's, Tukey's HSD, or Bonferroni, may be performed without a significant, "preliminary" one-way ANOVA (many of these tests were created to deal with multiplicity in general rather than be a "next step" to…
Yooperman
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