Questions tagged [tukey-hsd]

Tukeys Honest Significant Difference (HSD) is a multiple comparison method based on the studentized range distribution.

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19
votes
2answers
50k views

How can I get a significant overall ANOVA but no significant pairwise differences with Tukey's procedure?

I performed with R an ANOVA and I got significant differences. However when checking which pairs were significantly different using the Tukey's procedure I did not get any of them. How can this be ...
25
votes
1answer
64k views

Comparing levels of factors after a GLM in R

Here is a little background about my situation: my data refer to the number of prey successfully eaten by a predator. As the number of prey is limited (25 available) in each trial, I had a column "...
10
votes
1answer
892 views

Box plot notches vs. Tukey-Kramer interval

The "notch" help document (or original text) from boxplot in 'R' gives the following: If the notches of two plots do not overlap this is ‘strong evidence’ that the two medians differ (Chambers et ...
14
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2answers
97k views

How to obtain the results of a Tukey HSD post-hoc test in a table showing grouped pairs?

I would love to perform a TukeyHSD post-hoc test after my two-way Anova with R, obtaining a table containing the sorted pairs grouped by significant difference. (Sorry about the wording, I'm still new ...
7
votes
3answers
16k views

ANOVA results do not match post-hoc Tukey test, how to proceed?

There has been some discussion about why differences exist between factor significance after an ANOVA and no significance in the pairwise comparisons, and it has been very helpful. However, there is ...
2
votes
1answer
7k views

Significant ANOVA interaction but non-significant pairwise comparisons [duplicate]

I ran a two-way ANOVA and got a significant interaction. I ran a Tukey.HSD() post-hoc test in R and no pairwise comparisons were significant. Is this an error on my ...
1
vote
1answer
1k views

R Tukey HSD Anova: Anova significant, Tukey not? [duplicate]

i created a simple anova with three groups in R and get a significant Result. After that i do a Tukey HSD Test and now nothing is significant. How can that be? Pr(>F): 0.0316 Group | p adj 1 - 2 ...
9
votes
1answer
5k views

Two-sample $t$-test vs Tukey's method

Even if the $F$ statistic in an ANOVA test is significant, we may need to do further testing before drawing conclusions. The most common method for doing this involves the use of a multiple ...
4
votes
1answer
4k views

Why do planned comparisons and post-hoc tests differ?

I conducted a three-way independent ANOVA. I manipulated the sound of my stimulus to be 1: congruent (KON), 2: incongruent (INK) and 3: no sound at all (control condition). One of my planned ...
4
votes
2answers
803 views

Differing p-values car::Anova, anova & post hoc in logistic regression

I am currently working with a logistic model in R and I have a question regarding the p-values that I get from different types of tests. Since I have separation in my data (caused by X) I use the ...
4
votes
1answer
6k views

Does the Tukey HSD test correct for multiple comparisons?

After performing an ANOVA and then doing post hoc tests with a Tukey HSD test is it still necessary to correct for multiple pairwise comparisons or is that done already?
25
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4answers
34k views

Is there a nonparametric equivalent of Tukey HSD?

I am using JMP to examine differences in vegetation cover in growth form groups (trees, shrubs, forbs, etc.) before and after three treatments with a control. My sample size is small (n=5) and most of ...
11
votes
1answer
13k views

When to correct p-values in multiple comparisons?

I'm afraid that related questions didn't answer mine. We evaluate the performances of >2 classifiers (machine learning). Our Null hypothesis is that performances do not differ. We perform parametric (...
8
votes
2answers
9k views

Post-hoc test after 2-factor repeated measures ANOVA in R?

I have problems finding a solution regarding how to run a post-hoc test (Tukey HSD) after a 2-factor (both within-subjects) repeated-measures ANOVA in R. For the ANOVA, I've used the aov -function: <...
7
votes
1answer
37k views

Interpreting TukeyHSD output in R

I performed a simple ANOVA in R and then generated the following TukeyHSD() comparisons of means: I have a pretty good idea (I think) of what all this means except the 'p adj'. If I'm correct: The ...
2
votes
2answers
1k views

Post hoc test for Friedman test

I am running a Friedman test for my non-Gaussian data, on MATLAB. However, I am confused about the post hoc test to choose. Two concerns: (1) MATLAB's multcompare ...
4
votes
3answers
2k views

Meaning of “post hoc” multiple comparisons

My original thought was “post hoc” in a post hoc multiple comparison procedure means that the procedure is taken after an omnibus test (such as ANOVA F test) gives a significant result. But after ...
2
votes
0answers
1k views

Do only certain pairwise comparisons after significant interaction in two-way ANOVA

I am comparing measurements on a test group relative to a control group in three different environmental conditions. I am interested in both differences between environmental conditions and ...
1
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0answers
118 views

Multiple Comparisons Corrections within Subgroups

I've got a set of data points with "scores" that belong to a series of subgroups (not necessarily disjoint). That is, I may have a point that belongs to groups A, B, and D, and then another point that ...
3
votes
1answer
1k views

Interpretting non-contiguous significance letters from Tukey HSD test in the multcomp package? [closed]

I've only ever seen the compact letter display for Tukey's HSD give contiguous letter groupings but like in the following example this package is giving non-contiguous groupings (ie 'cde' is ...
2
votes
2answers
197 views

Why are there not obvious improvements over Tukey's method?

Is there a book that explains why there aren't better standard techniques than Tukey and ANOVA, for example? For comparison consider for example I read about the null hypothesis one-sample $t$ test ...
1
vote
0answers
210 views

Multiple ANOVAs, then multiple Tukey HSDs, correcting for multiple comparisons

My experiment has 5 conditions (let's say Treatment A, B, C, D and E). There are 12 measurements (let's say Measurement 1-12). I'm running 12 ANOVAs on the measurements, I assume this means I should ...
1
vote
1answer
3k views

ANOVA result indicated that there were sig. differences while Tukey post-hoc test revealed that there were no statistically sig. differences [duplicate]

I was conducted one-way ANOVA analysis to examone the level of knowledge shaorng among the employees based on there age differences. One-way ANOVA indicated that there were significant differences in ...