Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

Questions tagged [planned-comparisons-test]

29 questions
4
votes
1 answer

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 training. I have specific hypotheses stating…
JamesC
  • 53
  • 1
  • 3
3
votes
2 answers

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 with baseline alcohol intake as a covariate. I found…
Bevers1
  • 31
  • 2
2
votes
0 answers

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 significant ANOVA, and then in planned comparisons I'd…
user1205901 - Reinstate Monica
  • 11,303
  • 26
  • 77
  • 152
2
votes
1 answer

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 untreated, Aged treated. The hypothesis is that…
user120818
  • 121
  • 1
2
votes
0 answers

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 Hightreatment vs Low Treatment Or, as contrast…
Doctor David Anderson
  • 153
  • 1
  • 5
1
vote
1 answer

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 comparisons, and some of these comparisons are…
Phillip
  • 13
  • 2
1
vote
2 answers

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: If the data violates RM ANOVA assumptions (e.g.,…
user26473
  • 21
  • 2
1
vote
0 answers

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 experiment design in behavioral research, Roger Kirk,…
TTemplln
  • 11
  • 3
1
vote
1 answer

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). Thank you.
harico287
  • 35
  • 4
1
vote
0 answers

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: Call: glm(formula = nv ~ region, family = poisson, data = my_data) Deviance Residuals: Min …
harico287
  • 35
  • 4
1
vote
0 answers

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 this case Treatment is a factor (2 factors), Temp…
Nick Pardikes
  • 11
  • 1
1
vote
1 answer

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 make things simple, let's just say that in this…
intasker
  • 35
  • 5
1
vote
0 answers

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 the two contrasts built in the model. Condition…
Rtist
  • 223
  • 1
  • 5
1
vote
1 answer

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-sound) and product stimulus (Handtuch and TV) as…
Jens Stach
  • 149
  • 2
  • 9
1
vote
0 answers

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 germinated and my explanatory variables are treatment with…
Dario Fergnani
  • 11
  • 1
1
2