Questions tagged [planned-comparisons-test]

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Simple Contrasts versus Post Hoc Tests in repeated measures, which is preferred?

Planned Simple Contrasts versus Post Hoc Tests in repeated measures, which is preferred? Let's say I have a 10 (Week) x 4 (Group) repeated measures design and conducting a repeated measures ANOVA. My ...
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1answer
20 views

Is it appropriate/acceptable to do planned comparisons for data that will be submitted to a scientific journal?

I am currently analyzing data for an age-related neuroscience study with a 2x2 factorial design (treatment (2 levels) x age (2 levels)) yielding 4 total groups: Young untreated, Young treated, Aged ...
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19 views

Multiple comparisons among orthogonal contrasts

Do I need to make an alpha adjustment when testing planned orthogonal contrasts. While the contrasts are independent the same residual error is used. The author of a well regarded textbook on ...
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1answer
56 views

Should I use the package “emmeans” for planned comparisons? Or should it be used only for post-hoc tests?

Because "emmeans" looks at all pairwise comparisons, I am asking myself if I should use the package for planned comparisons (I have hypotheses about the differences between certain groups). ...
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Why do we need the package “emmeans” to compare between groups? Why don't we just calculate the confidence intervals?

I am conducting a Poisson regression to find differences between universities in 5 regions regarding the number of crimes occured there. The output: ...
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261 views

Pairwise contrasts for logistic regression in emmeans, back-transform or not?

I ran a mixed effects logistic regression in R (glmer). The model identified a significant three-way interaction that I am interested in decomposing using post-hoc multiple comparison in emmeans. In ...
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1answer
116 views

Repeated Measures MANOVA Planned Comparisons & Profile Analysis

I'm conducting a repeated measures MANOVA with one IV (4 conditions) and 2 DV's. My participants have taken each condition. Assuming the MANOVA and univariate tests are significant, I would like to ...
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1answer
134 views

Combining customized contrasts + nested ANOVA (?)

I would like to get some advice on running a customized contrast analysis. I have looked at a few vignettes and I think I get the basic idea, but I'm not sure how to adapt them for my purpose. To ...
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321 views

Can planned contrasts in ANOVA be one tailed tests?

I have an experiment with 3 within-subject conditions: A, B and C. My dependent variable is reaction time. I am interested in comparing A to B and A to C. Using aov() on R I run an one way ANOVA with ...
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1answer
340 views

ANOVA - significant main effect, no significant interaction. What to do next? planned comparison / post-hoc tests / simple effects?

I conducted a two-way ANOVA, with perceived diagnosticity, i.e. the ability to evaluate haptic properties of a product, as the dependent variable and sound manipulation (congruent, incongruent and no-...
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1answer
306 views

Negative Binomial „Ancova” with planned contrasts

My DV is count, obtained from psychological questionnaire (14 questions with options ”Yes”/”No”, each yes is 1 point, thus overall result is count of yeses). I’ve checked that Poisson distribution ...
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186 views

how can i do a priori (planned) contrasts for a 2 factors with interaction binomial GLM?

i´m new with R and i have a question to do. i´m doing a study on seed germination and i have trouble doing a priori contrasts for a GLM analysis. My response variable is proportion of seeds ...
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36 views

Comparing groups with different sample sizes

I have some data about network outages in two companies, by the type of machines they have: ...
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218 views

Reporting weights used in a priori planned comparisons APA style

My lecturer wants us to report in APA style the weights we used in a planned orthogonal comparison. I can't find this information anywhere, not in previous journal articles or APA publications. Can ...
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1answer
75 views

Multiple planned comparisons of frequencies (based on a binary DV and multiple IV's)

I'm looking for the most appropriate way to to conduct multiple planned comparisons of frequencies. I conducted an experiment in which participants could come from one of two groups, 'Group A' and '...
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2answers
215 views

Is a planned contrast significant if p is lower than .05 with no correction for multiple comparisons but higher than .05 with the correction?

I conducted a 2 x 4 within-subjects design experiment. I presented participants with unpleasant and neutral pictures and asked them to cope with their emotions in four different ways. Therefore, the ...
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46 views

Planned contrast through factor-based vs. model-parameter-based approach

I have two questions concerning planned contrasts: I would like to know how factor-based contrasts (obtained through an interaction term) compare to model-paramter-based contrasts (obtained by ...
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1answer
52 views

ANOVAS and Planned Comparisons

I'm fairly new to stats and we have been asked to conduct our own one way ANOVA's for class. Our first hypothesis is that gender will effect exercise. Our second is more one tailed, Men will ...
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70 views

Bayesian planned orthogonal contrasts, can one just average two means?

I have a dataset with three levels of one independent variable, repeated measures. To simplify, I have two planned contrasts to perform: High Treatment & Low Treatment combine, vs No Treatment ...
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1answer
427 views

Planned comparisons and experiment-wise error rate in factorial experiments

When using planned comparisons in the context of factorial experiments is it still necessary to compensate for the inflation of the experiment-wise error rate? My planned comparisons involve 4 ...
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1answer
277 views

Significant omnibus f-test but planned comparison testing showing no evidence of effect

i'm testing the relationship between four age groups of teachers on their perceived level of job security. I've run an omnibus f-test on some data, 240 subjects- no examples of any skewness, and it ...
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495 views

Independent t test significant but post-hoc planned analysis not

I was analysing two sets of data. In most cases for the study post hoc planned comparisons identified significance (<0.05), however for one sample, this was not achieved. However an independent t ...
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318 views

When an effect size has to be considered sufficiently large?

I submitted a paper in which I analyzed the data by a mixed design ANOVA. I reported generalized eta squared as effect size. After significant interactions, I conducted planned comparisons. A reviewer ...
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1answer
133 views

Partially orthogonal planned comparisons

I am comparing 8 means and want to set up a planned comparisons, rather than having my Bonferroni adjustment become overly-conservative in a post-hoc. For my groups I need to make a total of 16 ...
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1answer
3k views

Non-orthogonal planned comparisons: How to correct alpha?

I have a data set containing three groups (A, B, C). Group A and Group B have undergone two different types of training designed to improve the same thing. Group C is my control group with no ...
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212 views

One-way independent ANOVA where I expect two levels to be very similar and the other to be different. What's the right test?

I'm expecting Groups 1 & 2 to be very similar and Group 3 to be different. I'm using a very large data set and feel that power won't be an issue. Initially I felt that I'd then be expecting a ...
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2answers
2k views

A priori comparisons in a repeated measures design

I'm interested in finding out more about the use of a priori planned contrasts within a one-way repeated measures ANOVA design. Predictions: Grps 2+3 < Grp 1 Grp 2 < Grp 3 My questions are: ...
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2k views

Correcting for multiple comparisons on planned contrasts with an ANCOVA

I have done an experiment with 7 treatment conditions designed to reduce alcohol intake, and a control condition. The dependent variable is alcohol intake after treatment, and I have run an ANCOVA ...