Questions tagged [contrast]

The tag has no usage guidance.

1
vote
0answers
35 views

contrast for the interaction term

The link (How to setup and interpret ANOVA contrasts with the car package in R?) contains some code as you can see below, which gives an example of how to set up a contrast matrix based on a 2*2 ...
2
votes
0answers
149 views

Setting contrasts in lme4: contr.treatment vs contr.sdif [closed]

In my study, each participant completed the very same Reaction Time task 3 times in 3 Sessions. I am not entirely sure if I should code the variable "Session" using ...
2
votes
0answers
56 views

Can I predict future years if my model includes past years as a contrast variable?

I've fitted a model based on data from 2002 to 2013, treating year as a contrast variable. Year is one of several predictors. I would like to test it by asking it to predict() with newdata = ...
1
vote
0answers
196 views

Linear contrasts in SPSS - one-sided

I want to test a linear contrast (trend test) in SPSS with more than two groups. Let's assume my assumption is B>A>D>C. I did the coding of the contrasts manually and obtained a signficance level of ...
2
votes
2answers
3k views

Setting custom contrasts in R [closed]

I have a data as follows. ...
1
vote
1answer
254 views

Polynomial contrasts following a one way ANOVA

I have a small dataset that is amenable to trend analysis. Only 1 IV with three levels, a balanced design. Both the linear and quadratic contrasts came back as significant. What would be the ...
1
vote
0answers
37 views

Contrast Function in a time dependent cox model with interactions

I have a time-dependent cox model with three variables, each of which interacts with the other two. So my final model is: fit12<-coxph(formula = Surv(data\$TimeIn, data\$Timeout, data\$Status) ~ ...
2
votes
0answers
52 views

Testing simultaneous equality of contrasts

I have a one-way ANOVA model with 3 treatments. I have contrasts $\hat{\theta}_1=\hat{\mu}_1+\hat{\mu}_2$ and $\hat{\theta}_2=\hat{\mu}_3-\frac{1}{2}(\hat{\mu}_1+\hat{\mu}_2)$. I want to do a ...
1
vote
0answers
164 views

Contrast Estimates

Question: can I use contrast estimates to test a specific hypothesis if my model estimates are not statistically significant? I ran a HLM using SAS PROC MIXED where my model involves triple ...
0
votes
1answer
109 views

Obtaining all effects in a multinomial regression where the grand mean is set as baseline

I have data from these set of experiments: In each experiment I infect a neuron with a rabies virus. The virus climbs backwards across the dendrites of the infected neuron and jumps across the ...
1
vote
1answer
140 views

Using contrasts in Poisson regression

The question is about using contrasts in regression analysis (here, Poisson regression with robust error variance). We have divided the participants in our sample into 6 groups, according to their ...
1
vote
0answers
108 views

How to design a contrast matrix with a continuous variable

I was wondering if someone could help me designing a contrast matrix when you have a continuous variable. My model looks like this: ...
1
vote
1answer
2k views

Margins contrast after Tobit

I am researching firm level data. My endogenous variable is bounded from above and below. Thus I use a Tobit model to take account of the truncation. Among others I am interacting a continuous with a ...
6
votes
1answer
3k views

testing contrast in two-way ANOVA using multcomp

I am trying to compare two levels of a factor aggregated over the levels of another one using the multcomp package. I use a "between-subjects-version" of the dataset obk.long contained in the afex ...
0
votes
1answer
587 views

When should I use contrast coding?

I have a - so I guess - a simple question: I am using Stata 13 and I am running a Tobit model to understand differences in firm performance. Among others, I am controling for firm types $T_i$- i.e. ...
15
votes
2answers
17k views

Interpretation of betas when there are multiple categorical variables

I understand the concept that $\hat\beta_0$ is the mean for when the categorical variable is equal to 0 (or is the reference group), giving the end interpretation that the regression coefficient is ...
2
votes
1answer
173 views

Number of contrasts in an orthogonal contrast test

This is my first time asking a question here, so please let me know if anything is unclear. So I was trying to learn how to set up contrasts from this page, and here is the code: ...
2
votes
0answers
388 views

How do you test for trend in a generalized linear model, particularly for odd numbers of levels of a variable?

I'm trying to test for a trend across levels of a categorical variable using a contrast statement in a model and can not figure out how to do it when there are odd numbers of levels. Looking at SAS's ...