Tagged Questions
0
votes
0answers
33 views
Is my random variable affecting my response?
I performed an experiment on coral colonies (10 colonies, randomly chosen in repeated measurements); manipulating aragonite/carbon chemistry and temperature (fixed effect) to analyse effects on the ...
2
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0answers
19 views
Repeated measures ANOVA in R for non-orthogonal design
I have data from a two-factor within-subjects experiment design where the conditions are not orthogonal. Factor one (Location) has three levels; factor two (Stimulus) has three levels, one of which is ...
0
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1answer
35 views
Simple Mixed Model with 1 Fixed and 1 Random Effect
I have various datasets I need to analyse regarding soil properties, all in the same fashion, with one fixed effect (which is a position along a transect, indicating different land uses). Now my main ...
3
votes
2answers
105 views
Using lmer for repeated-measures linear mixed-effect model
EDIT 2: I originally thought I needed to run a two-factor ANOVA with repeated measures on one factor, but I now think a linear mixed-effect model will work better for my data. I think I nearly know ...
1
vote
0answers
32 views
GLM with unequal sample size
I am trying to figure out how to run a GLM with a poisson distribution in R. The data has 4 treatments: A(n=16), B(n=17), C(n=16), D(n=20), and 2 time periods. This data is count/area so there are ...
1
vote
1answer
32 views
Repeated-measures error in R ezANOVA using more levels than subjects (balanced design)
I'm having a problem running a repeated-measures ANOVA in R using the ezANOVA function.
I have data from 18 subjects - each subject participated in 3 conditions, ...
2
votes
1answer
62 views
Advice on the statistical analysis of clinical data using summary statistics, t-tests, ANOVA, and linear regression
I need some help with the statistical analysis of a study of a particular surgery to remove a particular cancer. I am using the statistical program R to conduct my analysis. My data are saved in the ...
2
votes
1answer
41 views
What factor (trials or blocks) to use in a repeated measures ANOVA
I am conducting a psycholinguistic experiment. Each trial consists of the subject responding to a word by pressing a button.The design of my experiment is as follows:
5 blocks of a 100 trials each ...
1
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0answers
35 views
what does R mean by “unbalanced design”?
I think this means an unequal sample in different conditions. But it seems to mean something else. . .
I have a data set like below
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0
votes
1answer
34 views
Efficient way to run multiple ANOVAs on subsets of data
I have a data set that is repeated-measures ratings of four devices (two two-level variables) for 6 dimensions (ease, confidence, comfort, control, size and fit), with a two-level between-subjects ...
4
votes
2answers
110 views
R p-value half to SPSS rANOVA
I have done rANOVA in SPSS and then in R and got two different p-values from the same model. While SPSS gives 0.032, R gives 0.0162, which when rounded is a half. Other data are exactly the same.
1. ...
2
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0answers
34 views
Pretest-posttest plus control design
I am evaluating the effect of an intervention (treatment: a lecture) on the ability to spot behavioral clues of emotions using visual stimuli using pretest-posttest plus control group experimental ...
0
votes
1answer
72 views
Question about reading an output for using ANOVA to compare two linear models
I tried to compare the following two models using "anova.lm()" in R:
...
1
vote
2answers
83 views
Difference between a 2 factor ANOVA and mixed effects model
The lme4 package in R includes the cake dataset.
...
1
vote
0answers
36 views
Variance associated with factors in GLS (nlme)
First time posting here, so thank you ahead of time for your help. I'd like to estimate the variances associated with two factors in a relatively simple, but unbalanced GLS model, and I am unsure how ...
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 ...
1
vote
1answer
57 views
How to interpret a non significant independent variable?
I conducted a regression analysis using R's lm() function. One of the independent variables shows no significance (p = 0.89), which contradicts the hypothesis that is should have a significantly ...
0
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0answers
63 views
How can I perform an ANOVA from multiple CSV files with R?
I (or rather, my girlfriend whom I'm trying to convert to free software) am just getting started with R.
She wants to do a two-way ANOVA on her data on mussels and the threads they release in ...
4
votes
1answer
173 views
R, Differences between lm and aov
What does explain the differences in p.values in the following aov and lm ?
Is the difference only due to different types of Sum of square calculations ?
...
0
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1answer
53 views
0
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0answers
22 views
Sphericity in GNU R for within subject design
I'm now trying to caliculate Mauchly's test, sphericity test for within subject design, using GNU R.
My data, Df4 is fellow,
...
0
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0answers
540 views
Tukey HSD on Two way ANOVA with Interaction
I saw an example online of a two way ANOVA followed by Tukey HSD using the ToothGrowth dataset in R (factorial, betwen subjects design), but don't know how to ...
0
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0answers
69 views
Should a mixed effects model be used?
This post provides an excellent example of the inner workings of a mixed effects model: http://emhart.github.com/blog/2012/11/16/making-sense-of-random-effects/
In a hypothetical study, I have ...
0
votes
1answer
106 views
Checking confidence intervals on user defined contrast (one-way ANOVA)
Hi is anyone able to help - I am doing this all in R Code:
I have run one way analysis on some data and set up 2 contrasts (Liberarts-Finearts and also Engineering-science). I now need to calculate ...
0
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2answers
168 views
One-way repeated measures anova
I tried finding an answer to this question on this and other sites but to no avail - if I am missing something please excuse my inability to locate the answer!
Basically I have several dependent ...
0
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0answers
105 views
two way repeated measures anova random factors missing data
I have a pretty simple time series experiment that I'd like to analyze in R. I have an experimental and control group and for each individual in each group I collected samples from them over a course ...
0
votes
1answer
133 views
How do I cross error terms in Stata's xtmixed (examples inside) like lmer's +(a*b*c|s)?
Let's say I have an experiment with three within-subject factors, A, B, & C. Data looks like this.
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3
votes
0answers
100 views
Specification of error terms in aov() in R
For a two-way repeated measures design, we can specify the model using aov in the following fashion:
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1
vote
1answer
305 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
259 views
Calculate F-statistic / p-value for subset of co-efficients in R
I'm wondering if there's an easy way of calculating an F-statistic / p-value for a subset of model coefficients. Particularly in R? I'm not sure what test would be needed to calculate this. For ...
0
votes
0answers
208 views
How to interpret R output for two-way repeated measures ANOVA
How do I interpret the following output from R for a two-way repeated measures ANOVA
...
0
votes
1answer
110 views
Between subjects repeated measures ANOVA in R - 5 brands, 11 measurements
In my research I have performed a series of measurements on 5 different brands of blocks. Each block has been inspected for deformation under incremental forces (20, 30, 40, 50, 60, 70, 80, 90, 100, ...
2
votes
1answer
177 views
How does anova.lm in R calculates “Sum Sq”?
I'm learning R and trying to understand how lm() handles factor variables & how to make sense of the ANOVA table. I'm fairly new to statistics, so please be ...
0
votes
1answer
93 views
Between group comparison for every level of within factor
If I use lme for mixed ANOVA as follow
...
1
vote
0answers
92 views
Test for significance in a time series using R
I've got a time series data set that looks at population numbers on a yearly basis, and I would like to know if there is a significant difference between certain years, and if so- which years are ...
1
vote
0answers
53 views
ANOVA post hoc with concerned about the sphericity
According to this post the best way to do post hoc analysis in ANOVA in R is t-test + ptukey. Because lme + glht "essentially assumes the sphericity assumption holds".
How are t-test + ptukey ...
4
votes
1answer
411 views
Post-hoc test after 2-factor repeated measures ANOVA in R?
I have problems finding a solution regarding how to run a post-hoc test (Tukey HSD) after a 2-factor (both within-subjects) repeated-measures ANOVA in R. For the ANOVA, I've used the aov -function:
...
1
vote
1answer
564 views
ANOVA or Regression? 1 Continuous factor & 1 Categorical factor with continuous response variables
I have 1 categorical factor (3 treatments) and 1 continuous factor (weight) and then I have 5 continuous response variables.
From what I have read, I should not use a two way ANOVA as one of the ...
0
votes
1answer
77 views
R loop for anova on multiple files [closed]
I would like to execute anova on multiple datasets stored in my working directory. I have come up so far with:
...
3
votes
1answer
246 views
Analyse unbalanced repeated measures 2x2x2x2 type II anova interactions
I have a run an unbalanced 2x2x2x2 Type II ANOVA in R and am having trouble following up on the results. Here is the output:
...
0
votes
0answers
69 views
Type of ANCOVA design in R
I have the dataset that contains one continuous measure of plant leafs (PC1 scores of individual leafs), that is dependent variable and three others that I need to use as independant, explanatory. One ...
3
votes
2answers
449 views
How would you do Bayesian ANOVA and regression in R?
I have a fairly simple dataset consisting of one independent variable, one dependent variable, and a categorical variable.
I have plenty of experience running frequentist tests like ...
1
vote
1answer
100 views
anova(model1, model2) vs. anova(model2, model1) in R
I'm trying to figure out why there is a difference when I run anova(model1, model2)
versus anova(model2, model1) in R. I know ...
2
votes
2answers
162 views
Partial, adjusted or Type-III SS of factorial experiment in R
The partial SS for two factor (N and P factors) factorial experiment with interaction can be calculated as:
\begin{eqnarray*}
\textrm{SS}\left(N_{i}|\mu,P_{j},\left(NP\right)_{ij}\right) & = ...
7
votes
1answer
687 views
Nested/SplitModel - RepeatedMeasures/MixedModel ANOVA: levels of nesting & scripting in R
My data set has the following variables:
Treatment (4 types- fixed)
Location (8 locations- fixed)
Position in Location (3 positions per location- fixed)
Samples are taken in each position (3 ...
2
votes
2answers
195 views
R model.tables() incorrect means – possible bug?
I was doing ANOVA in SPSS and then in R and to my huge surprise, the results from the latest version of R were incorrect.
When I use the function ...
1
vote
0answers
68 views
How to analyze differences of two groups with replicates?
I am trying to see if there are differences between two groups (background genetic mutants) and some values associated to them. Every group has 4 different gene types with two replicates each and its ...
0
votes
1answer
131 views
Question with R and repeated measures
Second time I'm turning to this site, it has helped before. I am looking for some coding help to perform a repeated measures anova in R. I have a total of 4 treatments, each replicated 3 times. They ...
1
vote
1answer
212 views
Why does a mixed design using R's aov() need the between subject factors specified more than once?
An R cookbook http://wiki.stdout.org/rcookbook/Statistical%20analysis/ANOVA/ has an example of using aov() for mixed design ANOVAs.
I'll copy it here:
...
1
vote
1answer
177 views
Can higher level be insignificant but lower level significant in a nested ANOVA?
I have ran a nested ANOVA on a data set and the results suggest that there is an association for the higher level with an insignificant P-value but also an association for the lower level with a ...
