Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

Questions tagged [dunnett]

Dunnett's test is a multiple comparison procedure for comparing a sngle control group with many comparison groups.

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Dunnett's test with unequal variances

I would like to compare t treatments against a single control using Dunnett's test. My problem is that the variance is not homogeneous across the treatments. Is it a problem for Dunnett's test? If so, which method is recommended? some R code…
user7064
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Mann Whitney U test or Kruskall-Wallis + Dunn test as a post hoc?

I performed a set of inhibition experiments where Lactobacilli supernatants where tested against a pathogen cell culture. These experiments were carried out in a 96-well plate where pathogen was cultured alone (control), 11 technical replicates, and…
Neuls
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Dunn test and specific comparisons

What I need is a non-parametric alternative for Dunnett test to compare several groups with a control group (not all pairwise comparisons). And I realise that a specialised test is more appropriate than multiple Mann-Whitney test because it would…
lapotok
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Do I have to correct for multiplicity twice if I re-run a comparison with one more hypothesis during incremental testing?

Let's say I have a set of hypotheses ordered in time. These are about comparison to some baseline moment: $H_{t1 vs. baseline}$, $H_{t2 vs. baseline}$, $H_{t3 vs. baseline}$, ... I have 10 time points, thus, 10 hypotheses. I want to find the first…
Gerard
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Is it possible to "reverse" the Dunnett post-hoc test: 1 treatment vs several controls?

I have 4 groups of patients who received Hepatitis B vaccines (based on different vaccination policies) a group too old to have received it. One of the policies was not properly implemented and the the corresponding patients have smaller antibody…
user2053921
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Planned contrasts in split-plot experiment

In a split-plot experiment, is it appropriate to use contrasts to compare mainplot-subplot combination treatments? And if so, how might I calculate the standard error of the contrast?
teakayist
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Is the "mvt" (using the multivariate t distribution) accepted way of adjusting for multiple comparisons when reporting to journals?

I use the awesome package multcomp and emmeans in R. These are the places I heard about the "mvt" method for the first time. And, however, it is what it's actually done in the Dunnett or Tukey method (just different contrasts, all-vs-control and…
GibbsSampler10
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Is there any measure of Effect Size for differences assessed with Dunnett method?

I know I could use the effect size pairwise, but I have a longitudinal data, where subjects were measures multiple times and there exists ICC > 0.5. I guess the pooled SD may be altered by this fact at each time point. Is there any dedicated…
Arianella
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Should I choose single model A+B+A:B or two models A at 2 levels of B?

I have a longitudinal model: response ~ device * time. The device should lower the response over time. There are two devices: A and B. There is an interaction between the device and time. The problem is that the model fit using GLS estimated using…
Katikarnata
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How is the classic Dunnett test, with strict assumptions, related to Dunnett comparisons run on a top of very liberal models, like GLM or GEE?

As far as I understand, the classic Dunnett test is based on the t-test, applied multiple times to all comparisons vs. control and then corrected. So the assumptions of the Dunnett test must agree with those for the t-test. Normal distribution,…
Kazakh
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How is the classic Dunnett test, with strict assumptions, related to Dunnett comparisons run on a top of very liberal models, like GLM or GEE?

As far as I understand, the classic Dunnett test is based on the t-test, applied multiple times to all comparisons vs. control and then corrected. So the assumptions of the Dunnett test must agree with those for the t-test. Normal distribution,…
Kazakh
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How to use Dunnett's test to detect the significant difference from two control groups?

I have a trait data set including two parents and one hundred offspring. I want to see whether the trait of the offspring are significant falling out of the trait ranges of the two parents. So I was thinking to use Dunnett's test to do this…
Zzzz
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How to compare several means to control when the distribution is not normal and sample sizes are unequal?

I have a large dataset (n = 170,000), distributed roughly equally among 5 groups (each is 34,000 ± ~1,000). I want to compare whether the means in any of the first 4 groups are different from the control. Before the data came in, I figured the best…
Khashir
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Does ANOVA work with percentages, like Conversion Rate?

I'm trying to figure out if I can perform ANOVA on conversion rate. Would this work? Editing for more information: The question we are trying to solve is for our AB Testing program. Oftentimes we have multiple variants within our tests, and we are…
Chad Sanderson
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