The contrasts tag has no wiki summary.
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How to Partition An Interaction SS in ANOVA
I'm a new user of R and I'm trying to replicate Table 6.18 on page 262 in Statistical Procedures in Agricultural Research, By K. A. Gomez and A. A. Gomez. New York, Chichester, etc.: Wiley (1984). ...
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34 views
How to avoid regression to the mean in a simple comparison
This is a pretty simple question but I haven't been able to find a clear answer to it. I have some data from a behavioral experiment taken under two conditions (A and B); within each condition, each ...
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1answer
99 views
Plotting predicted values in GLM in R
I am trying to find a more aesthetic way to present an interaction with a quadratic term in a logistic regression (categorisation of continuous variable is not appropriate).
For a simpler example I ...
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0answers
31 views
Checking for differences in time trends
I have two waterbodies that were sampled for a single water quality variable over time. Both waterbodies were sampled in the fall of each year from 2009-2012. In each year of sampling, 5 replicate ...
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15 views
orthogonal contrast with an ordinal variable in gam
I am fitting a set of continuous and factor variables into a GAM. The factors are ordinal: they are levels of abundance of specific macroinvertebrates set as "none" (0% cover), "low" (>0-10% cover) ...
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1answer
107 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 ...
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1answer
171 views
How to specify a contrast matrix (in R) for the difference between one level and an average of the others?
I have a regression model that looks like this: $$Y = \beta_0+\beta_1X_1 + \beta_2X_2 + \beta_3X_3 +\beta_{12}X_1X_2+\beta_{13}X_1X_3+\beta_{123}X_1X_2X_3$$
...or in R notation: ...
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0answers
130 views
How do I conduct an analysis of an interrupted time series design with a comparison group?
I am not sure if this is the right place to ask this question (if not, please refer me to the right place), but it would be nice if someone could help me:
Description of the Data/the Scenario:
I ...
3
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2answers
282 views
Effect size in contrast analysis
I'm running 2-way repeated measures ANOVA (3 and 5 levels) with planned contrasts afterwards. I'm interested in comparing
1)levels of the first factor among themselves (e.g. A1B with A2B, A2B with ...
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2answers
109 views
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1answer
136 views
Questions about the glht function for planned comparison
I have a nested model with the following effects
fixed: treatments
random: experiment_date
I used lme() to model the data
...
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0answers
154 views
Orthogonal contrasts in R
I am having somewhat of a problem setting up contrasts from an anova in R. I have done this in the past, but at the moment I don't seem to be able to get R to use my contrast matrix instead of the ...
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2answers
412 views
Contrast for hypothesis test in R (lmer)
I'm running a lmer mixed effects model with a four-level factor (levels "0","10","100","1000") as the fixed effect.
lmer(free ~ reward.f + (1|S), longdata)
I ...
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1answer
298 views
Contrasts in repeated mesures ANOVA in R
I am a refugee from SPSS in the process of re-learning how to do everything in R. Mostly it's been fun, as R is great for a lot of things but I've run into a snag that I can't seem to find a solution ...
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1answer
294 views
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0answers
303 views
Calculating standard errors for contrasts of parameter estimates of a (multiple) linear regression
I am running regression analyses in matlab with glmfit and calculate significance of contrasts of parameter estimates by using standard errors. Somehow however, the results I get are not consistent ...
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0answers
237 views
Seeking an effect-size measure for simple effects in binary logistic regression in SPSS [closed]
I am trying to get an effect-size measure for simple effects in a binary logistic regression. I am using the GENLIN procedure in SPSS; here is the syntax:
...
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1answer
169 views
Non-significant MANOVA with significant planned contrasts [duplicate]
Possible Duplicate:
Not-significant F but a significant coefficient in multiple linear regression
How can you have a non-significant multiple regression model w/ significant predictors?
...
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2answers
295 views
How to interpret these custom contrasts?
I am doing a one way ANOVA (per species) with custom contrasts.
...
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2answers
197 views
Refugee from SPSS having issues with fit.contrast in R
I'm trying to wean myself off of SPSS and switch to R for psych statistics and I'm mostly getting there, but I've run into a real roadblock with fit.contrast from ...
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2answers
443 views
Confused about sum and treatment contrasts
I'm currently studying for an Experimental Design exam. I feel like I'm missing something quite fundamental...
I've attached a minimal example to illustrate my confusion at ...
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0answers
140 views
How to test and examine interaction effect in 2 by 3 by 6 mixed ANOVA design?
Background:
I have two groups of children - one group with normal hearing and one with permanent hearing losses - call them NH and PHL.
Each child has had a hearing test, consisting of 6 different ...
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2answers
3k views
What if an overall ANOVA is not significant, but specific contrasts are?
Study Design: I have a 2x3 factorial design, 2 levels of Time (2050 or 2100) by 3 levels of information (None/Control, Moderate, Extreme).
I set up some very specific contrasts when analyzing this ...
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1answer
226 views
What are the different types of codings available for categorical variables (in R) and when would you use them?
If you fit a linear model or a mixed model there are different types of codings available to transform a categorical or nominal varibale into a number of variables for which paramaters are estimated, ...
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3answers
1k views
How to do post-hoc tests with logistic regression?
I looked at whether participants recycled after being subjected to a given message. There were three groups: a Control group, group A, and group B.
Since my dependent measure was dichotomous ...
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0answers
77 views
Weighing contrasts differently for unbalanced designs
I'm using a mixed effect multilevel model for a crossed design in R. By design, one of my conditions has half the number of observations as the other condition (I am not talking about missing values ...
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3answers
484 views
How to apply coefficient term for factors and interactive terms in a linear equation?
Using R, I have fitted a linear model for a single response variable from a mix of continuous and discrete predictors. This is uber-basic, but I'm having trouble grasping how a coefficient for a ...
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2answers
5k views
How do you report significant contrast results for a MANOVA in APA style?
Do you just report that MANOVA significance test is significant, or do you have to include contrast estimates (SPSS K MATRIX)? In the latter case, what are ...
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1answer
137 views
Conditional regression for 2 SD below / above the mean
I want to interpret an interaction. Usually a conditional regression analysis is done with 1 SD below/above the mean (see Aiken & West, 1993, p. 18). My result is a contrast with $p=.068$ if I ...
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159 views
Chi-squared planned contrasts comparison adjustment problem
I have Group A, B, C. My hypotheses are:
1) proportions of C are different from proportions of B (=independance)
2) proportions of A are NOT different from proportions of B (=NO independance)
...
3
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1answer
336 views
Chi-square contrast tests with R
I have Group A, B, C.
My hypotheses are"
1) proportions of C are different from proportions of A (=independance)
2) proportions of C are different from proportions of B (=independance)
3) ...
3
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1answer
163 views
How to design a contrast matrix with combined levels for a categorical variable?
I wish to make a contrast matrix in the case of a linear model.
I have one factor with three levels: T, N and ...
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0answers
258 views
Contrast to ANOVA with interaction term
I need to fit orthogonal contrasts to the following model. The following example data.
...
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3answers
322 views
Sidak correction
For variables A (product research) and B (product purchase), I am proposing to do three levels of analysis as follows:
Test 1: Overall:
The goal here is to see if there is a relationship between A ...
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1answer
196 views
How to find a confidence interval for a contrast?
I have a latin square with a particular treatment; I have done a contrast so I have a value for the mean of the contrast $$\hat \theta_1 = \mu_1-\frac{1} {3}(u_2+u_3+u_4) \>.$$
I also have a ...
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1answer
775 views
How to perform a 4 by 4 mixed ANOVA with between- and within-subjects contrasts using R?
Beginner user of R here struggling with a repeated measures ANOVA.
I have a dataset that consists of one between subjects factor with 4 levels (coded in a single variable called 'groups'), and one ...
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2answers
2k views
How to specify specific contrasts for repeated measures ANOVA using car?
I am trying to run a repeated measures Anova in R followed by some specific
contrasts on that dataset. I think the correct approach would be to use
Anova() from the ...
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3answers
330 views
Are linearly dependent contrasts permitted when performing planned comparisons in within-subjects ANOVA?
Here it says that planned comparisons should be linearly independent.
Here (page 13) and elsewhere I see people giving examples of linearly dependent contrasts.
How should this conflicting advice ...
6
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1answer
5k views
Post hoc test after ANOVA with repeated measures using R
I have performed a repeated measures ANOVA in R, as follows:
aov_velocity = aov(Velocity ~ Material + Error(Subject/(Material)), data=scrd)
summary(aov_velocity)
...
4
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1answer
969 views
How to setup and interpret ANOVA contrasts with the car package in R?
Let's say I have a simple 2x2 factorial experiment that I want to do ANOVA on. Like this, for example:
...
3
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1answer
1k views
Recommended effect size measure for repeated measures t-tests and repeated measures contrasts on experimental data
Context
This came up recently in a consulting context. A researcher was performing repeated measures t-tests based on experimental data.
Some of the analyses involved comparing one condition with ...
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0answers
272 views
Tutorial for performing Contrasts for MANOVA
Context
I have a multivariate dataset with a test group and three control groups.
I was thinking that the best way to determine if and how the test group differed from all of the control groups would ...
3
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1answer
1k views
Post hoc comparison in two way ANOVA with covariate using R
Does any body know how to run a post hoc comparison in a 2X2 ANOVA with covariate in R. multcomp package seems very nice but I could not find clear answer or example to my question with this package. ...
3
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1answer
822 views
Test for interaction contrasts using Prism or R
Please reference this question (stats.stackexchange.com) http://bit.ly/got8Bs for study design and initial reply from caracal.
My question now is: How can I test for an interaction contrast between ...
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4answers
4k views
How does one do a Type-III SS ANOVA in R with contrast codes?
Please provide R code which allows one to conduct a between-subjects ANOVA with -3, -1, 1, 3 contrasts. I understand there is a debate regarding the appropriate Sum of Squares (SS) type for such an ...
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3answers
1k views
Linear model with constraints
I'm quite new to R and I have a following problem:
I have a simple 2-factor linear model:
...
