Linked Questions
38 questions linked to/from Do we need a global test before post hoc tests?
4
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Use of "post-hoc" tests - do these require an ANOVA to be performed first? [duplicate]
I would like to compare multiple means using a method such as an ANOVA. This would have to be followed up with either Scheffe's test or the Games-Howell post-hoc method (my data is non-normal - to ...
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1
vote
0
answers
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Corrected multiple comparison: is the preceeding ANOVA necessary at all? [duplicate]
To compare multiple groups, one usually runs ANOVA. If ANOVA rejects the null hypothesis, one goes through the multiple comparisons.
The multiple comparisons are necessary to establish which group is ...
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2
votes
0
answers
72
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Why do we conduct one-way ANOVA instead of jumping right into multiple comparisons if we have a simple, single main effect dataset? [duplicate]
This question is for simple data structure that involves one main effect only. I can definitely see ANOVA's usefulness in more complicated data containing multiple effects.
Aside from being a "...
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35
votes
4
answers
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Can ANOVA be significant when none of the pairwise t-tests is?
Is it possible for one-way (with $N>2$ groups, or "levels") ANOVA to report a significant difference when none of the $N(N-1)/2$ pairwise t-tests does?
In this answer @whuber wrote:
It is ...
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23
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3
answers
72k
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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 ...
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8
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3
answers
1k
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Non-significant results when running Kruskal-Wallis, significant results when running Dwass-Steel-Critchlow-Flinger pairwise comparisons
I am writing my Master's thesis on adult's performance on cognitive and linguistic measures. I have four age groups and am investigating if there is an age difference in the performance on summarized ...
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24
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1
answer
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Why use ANOVA at all instead of jumping straight into post-hoc or planned comparisons tests?
Looking at a between-groups ANOVA situation, what do you get by actually doing such an ANOVA test first, and second do post-hoc (Bonferroni, Šidák, etc.) or planned comparisons tests? Why not skip the ...
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10
votes
3
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14k
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Relation between omnibus test and multiple comparison?
Wikipedia says
Methods which rely on an omnibus test before proceeding to
multiple comparisons. Typically these methods require a significant ANOVA/Tukey's range test before proceeding to ...
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8
votes
4
answers
3k
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Strange result of post-hoc test
I have data for a test on three groups. The measured variable is ratio scaled. The R code is
g1a<-c(7, 3, 40)
g2a<-c(1,1,2)
g3a<-c(0,0,0)
Since the ...
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4
votes
4
answers
2k
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Repeated measures ANOVA with significant interaction effect, but non-significant main effect
I am running a two-way repeated measures ANOVA (main effects: Time, Condition). The result is that the main effect of time is significant (P<0.05), the main effect of condition is not significant (...
4
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3
answers
6k
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Non-significant Kruskal-Wallis and significant post hoc tests
I have done this analysis where in Figure A-D. the Kruskal-Wallis global p-value is non-significant, but the p-value for pair CS and SCS in Figure A however is significant (at P<0.05). I read ...
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10
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3
answers
5k
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Is there a consensus on adjusting alpha for multiple contrasts if the main effect is significant?
After talking to a couple of statisticians, reading some book sections, internet articles, and forums like this, I am still unclear about multiplicity adjustments of post hoc tests and contrasts.
Let'...
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8
votes
2
answers
12k
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If only a two-way ANOVA main effect is significant, what is the appropriate follow-up?
What (with justification) is a valid post-hoc for a two-way ANOVA main effect, if no interaction is present?
Example two-way fixed effect ANOVA:
...
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12
votes
1
answer
5k
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What question does ANOVA answer?
I want to learn ANOVA. Before I start to learn how the algorithm works (what calculations have to be done) and why it works, I first would like to know what problem do we actually solve with ANOVA, or ...
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1
vote
1
answer
5k
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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 ...
1
vote
1
answer
3k
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What type of hypothesis test for multivariate testing (Website)
Situation:
A website I work on has the following funnel:
Home page (landing page) > pricing page > create account > convert (subscribe with credit card).
We ran a test on the pricing page. There were ...
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3
votes
1
answer
1k
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What is more powerful – an ANOVA test or post hoc tests?
From answers on this site I have learned that it is possible to get significant results from multiple comparison tests ("post hoc"), even if ANOVA did not yield a significant result. I ...
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6
votes
2
answers
315
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Post hoc contrasts when only certain contrasts make sense
My experiment has a 2x2 design, full between-subjects, so that the resulting four groups are as follows:
-Group A-1: Experimental treatment A.
-Group A-2: Control for experimental treatment A.
-Group ...
2
votes
3
answers
2k
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Correction for multiple comparisons
I have a 2x3x4 repeated measured anova. I have a significant 3-way interaction, and I want to make sure that I am using the correct post hoc comparisons and not violating any key statistics theory.
I ...
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2
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0
answers
3k
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lsmeans multiple comparisons and Fishers LSD
I am using the lsmeans package for "post hoc" multiple comparisons and I read here: ANOVA - Do we need a global test before post hoc tests? that in general post hoc ...
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1
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0
answers
2k
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How to report significance of factor levels shown in summary of glm?
The summary of my GLM shows day 12 of factor Date to be significant, but anova(model, test="Chisq") shows Date to be not significant overall. I know how to report the statistics from the Chisq table, ...
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0
votes
0
answers
879
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Interpretation of discrepancy between prop.test and pairwise.prop.test results
My aim is to find out if infection state (pos / neg) is associated with the group of patients (A, B or C). For this analysis I have followed suggestion from How to analyze $ 2\times n$ contingency ...
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2
votes
2
answers
499
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T- test for A, B, C, D
As you know, Student´s t-test is only valid for a pair of variable/experiment.
for instance, we can do t-test(A, B).
Now, I need to test whether variables A, B, C, D are close to each other or not. ...
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0
votes
0
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493
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Conclusion on which groups differ without doing post-hoc test
If you do a statistical test that compares groups and find a significant difference between groups, can you then conclude that there is a difference between the "lowest" group and the "highest" group, ...
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2
votes
1
answer
255
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Discrepancy between the results of the ANOVA and the post-hoc test: How should be such results interpreted and presented?
It is possible to find discrepancies between the results of ANOVA and post-hoc tests. The results of post-hoc tests are valid (with the exception of the Fisher LSD test) even if the overall P value ...
1
vote
1
answer
249
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qqplot result and normality for ANOVA
The independent variable is promotion, and it is assigned to 3 groups. The dependent variable is sales revenue. I have 172 observations of sales revenue for promotion group 1, 188 for group 2 and 188 ...
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2
votes
1
answer
272
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Multiple testing adjustments in posthoc.quade.test
In R, posthoc.quade.test (package PMCMR) or quadeAllPairsTest (the new variant, PMCMRplus) are posthoc tests for Quade test and offer the option for adjustments (i.a. Holm, BH etc.).
In my previous ...
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0
votes
1
answer
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Choosing the right test to compare the difference in mean between 3+groups according to the data we have (param vs non-param, sample size..) [closed]
I hope everyone who reads this is fine. I come to you for help, I am a student in data analysis, but I am not yet familiar with everything, especially regarding tests.
I have 3 groups of independent ...
user292504
2
votes
1
answer
108
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Factorial regression without significant interaction - can I consider contrasts significant?
First, I'm really sorry if this is a duplicate, I just couldn't find a definite answer.
I'm not used to analyzing categorical variables so I'm having trouble with something that is probably very basic....
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3
votes
0
answers
106
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Difference between one-way ANOVA and all pairwise comparisons with Bonferroni correction [duplicate]
If you have five groups and you wish to know if there is a significant difference between any of the group means, you would have to do 10 pairwise comparisons to test all possible pairs of means. You ...
user46925
1
vote
1
answer
55
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What statistic to use
My 8 year old daughter is conducting an experiment to assess memory. She has 3 groups. Condition 1, Condition 2 and ...
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2
votes
3
answers
66
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compare weighted coins
I have n (much larger than 2) coins that can give Head or Tail in a toss. For each coin, I have one sequence of trials which may have different lengths. For example, a conceptualized dataset could ...
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1
vote
1
answer
68
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Repeated measures ANOVA modeling question
I have a (to me) complex experimental design I'm working on pre-registering and I want to make sure I'm approaching the model correctly. I've attempted to offer an illustration of the design below.
I ...
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1
vote
1
answer
85
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Linear regression on categorical variable, how to interpret the F-statistic?
I am using statsmodels to fit a regression:
smf.ols(formula=change ~ C(location))`
where change is a continuous variable.
I have a lot of locations and some of the ...
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0
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0
answers
83
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Mixed logistic regression with glmer on R: better to use summary(model) or Anova(model) with 3-level factor as predictor?
I'm running a mixed logistic regression on a dichotomous variable in R with glmer, with two fixed effects in interaction: one is a factor with two levels, and the other is a factor with three levels. ...
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0
votes
1
answer
55
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Is it possible to use least significant differences even if my oneway ANOVA (9 steps) is not sig?
I ran an oneway ANOVA with 9 steps. In the options I clickt the LSD post-hoc test.
In Andy Fields Statistics Book there is a hint that LSD requires the overall ANOVA to be sig. But it doesn't tell ...
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1
vote
0
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Planned comparison in the absence of significant interaction
this is a topic that has been discussed in other posts, but there was never a direct answer to my question.
I have a dataset whereby my dependent variable is predicted by three categorical factors of ...
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1
vote
1
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Is it possible to conduct post hoc eventhough there is no significant interation between the levels of factors in lmer results?
I want to conduct a statictical analysis on reation times(dependent) between two groups of people.
suppose the factors are: A, B, group
Is it possible for me to conducting a posthoc test(by using ...
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