Tagged Questions
1
vote
3answers
37 views
When do Post-hoc tests require an adjustment for multiple comparisons
What happens to the Type 1 error rate, the Type 2 error rate, and Power if you do
not adjust for multiple comparisons when you should? What happens to these as a result
of using something like ...
0
votes
0answers
64 views
Analysis to use with categorical response and categorical predictor variables
I have data from a randomized survey experiment in which each respondent was assigned to one of 4 groups, one of which can be considered a "control" or "no treatment" group. The key question asked in ...
4
votes
0answers
61 views
Comparing models of different types of ANOVA - multiple comparisons?
Statistical semi-novice question:
Just following up this question, the fact that the three types of ANOVA exist with an unbalanced design, and that (presumably) you don't necessarily know a priori ...
1
vote
1answer
288 views
Two questions about Bonferroni adjustment
I have two questions about Bonferroni adjustments:
1). Can one use the Bonferroni method to compare independent groups? The reason why I ask this is it seems that many examples I've encountered ...
4
votes
2answers
213 views
What is the correct way to choose tests for pairwise comparison after ANOVA?
I am measuring secretion of insulin upon glucose stimulation of pancreatic islets after various treatments.
So I have two independent variables/factors:
Treatment (three different compounds and a ...
1
vote
0answers
112 views
Survival analysis w/ repeated observations of experimental and control units within periods of differing size & trends over the periods
I have an experiment called Fear Conditioning Acquisition Protocol. We expose mice to subsequent white sounds followed by short electric shocks through the floor. Our aim is to let them learn to ...
1
vote
1answer
59 views
Regression and multiple comparison methods for data where each available category is ranked
I have collected a data from 200 customers on their brand preference of 5 international fast food chain shops. Each customer was asked to rank all the 5 brands from highest to lowest (5 for the most ...
4
votes
2answers
286 views
How to run a two-way ANOVA with a random variable followed by pairwise comparisons?
I have a dataset with which I would like to compare the effect of species and habitat on movement rate, with pairwise comparisons. I would also like to include the effect of individual (as a random ...
2
votes
1answer
141 views
Repeated measurements with missing values
The data is measured in two biological replicates with two technical replicates, each.
Each variable might be detected only in one or more replicates, in the others it is considered missing at ...
1
vote
1answer
627 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?
5
votes
2answers
5k 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 ...
3
votes
1answer
341 views
Use of “post-hoc” tests - do these require an ANOVA to be performed first?
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 ...
4
votes
2answers
1k views
Bonferroni and Greenhouse-Geisser corrections with repeated-measures ANOVA
I guess my question comes in two parts:
Following a 1x7 repeated-measures ANOVA, I carried out 3 pre-planned tests. Two were t-tests between 2 of the conditions. The third is a 1x6 ANOVA (to test ...
3
votes
2answers
531 views
Experimentwise alpha for 2-way ANOVA
A two-way ANOVA yields 3 F ratios. Each F ratio has alpha of .05. Does that mean the experimentwise alpha level of the ANOVA is not .05 but rather is 1 - .95^3? If so, is there a recommended way to ...
0
votes
1answer
78 views
Multiple measurements within groups test
I am measuring the X, Y, Z variables of i subjects in k states, and for each subject and state i am taking j measurements. What is the proper way to test for differences between the k states?
It ...
2
votes
1answer
966 views
Cohen's d and multiple comparisons for 2/3-way ANOVA
I am conducting three-way ANOVA (A*B*C) with 2 levels each.
1) I found A*B interaction.
2) I moved to 2-way ANOVA (A*B) and found interaction again. I reported Eta-squared and equivalent Cohen's d.
3) ...
4
votes
2answers
792 views
Multiple comparisons with ANOVA including one between and one within-subject effect
I'm trying to look at multiple comparisons (across levels of my between subjects factor) for a model with one between-subject factor and one within-subject factor. I was trying to use TukeyHSD on an ...
4
votes
1answer
96 views
Mean of one group vs. the rest of the sample
I have data from a survey with Likert-type questions (Rate how strongly you feel about this issue on a scale from 1 to 10).
We know the respondents home town (as well as some other information, such ...
7
votes
1answer
223 views
What article or book clearly states that one can't use protected t-tests in within subjects ANOVA?
I have been asked to use protected paired samples t-tests in an analysis. The requester states that if I do not use the overall MSe from my (1 factor with four levels) within-subjects ANOVA when ...
7
votes
2answers
747 views
Correcting for multiple comparisons in a within subjects / repeated measures ANOVA; excessively conservative?
It strikes me that the available corrections for multiple comparisons in the context of a repeated measures ANOVA are excessively conservative. Is this actually the case? If so, what are some ...
3
votes
1answer
469 views
Can I have an example of pairwise comparisons of data against a within-subject factor?
Here is an ANOVA model with one between-subject factor (condition; 4 levels) and one within-subject factor (trial_seq; 20 levels).
...
6
votes
4answers
852 views
If a statistics doesn't reveal a significance do I have to calculate power for it?
Following the design and data described in this question, I did a simple one-way within-subjects repeated-measures (RM) ANOVA and found some significant p-values. I then applied non-orthogonal ...
4
votes
2answers
541 views
Uncorrected pairwise p-values for one-way ANOVA?
I'm performing a relatively simple one-way ANOVA as part of a class exercise. I'd like to get pairwise uncorrected p-values out of R, so I can do a sequential FDR test in another package (I realize ...
11
votes
1answer
6k views
Bonferroni or Tukey? When does the number of group means become large?
Reading Field's Discovering Statistics Using SPSS 3rd Edition I was struck by a bit about post hoc tests in ANOVA. For those wanting to control the Type I error rate he suggests Bonferroni or Tukey ...
4
votes
1answer
270 views
ANOVA and multiple testing correction in gene screening
I want to discover which genes are expressed in only one of five treatments. This is my pipeline:
ANOVA between the five treatments
Holm multiple testing correction
Tukey for significant genes ...
3
votes
1answer
110 views
Statistical analysis of mutant proteins sequences
Let's say that there is a table like the one below, where for each mutant (A, B, C, etc.) protein or peptide we have a binding and a functional information (true/false) column, and for each amino acid ...
9
votes
2answers
4k views
Multiple comparisons on a mixed effects model
I am trying to analyse some data using a mixed effect model. The data I collected represents the weight of some young animals of different genotype over time.
I am using the approach proposed here:
...
5
votes
2answers
2k views
If an ANOVA indicates no main effect and no interaction, should the lack of interaction be stated?
I measured response variable $Y$ at three levels of factor $A$ and four levels of factor $B$, $n=6$ reps/treatment. Results include
$A$ has strong effects on $Y$.
$B$ has no effect on $Y$
There is ...
8
votes
3answers
3k views
Post hoc tests in ANCOVA
Question:
What is a good method for conducting post hoc tests of differences between group means after adjusting for the effect of a covariate?
Prototypical example:
Four groups, 30 participants ...
4
votes
2answers
2k views
