# contrast analysis

1. ### Polynomial (quadratic) contrasts: clarifications & inverted-U

Hello everyone, I am trying to see how the motor time of a response to a stimulus (DV: quantitative, continuous) evolves based on difficulty level of the task (IV: 8 levels, categorical). My hypothesis is that motor time will increase, then decrease (inverted U shape). I conducted a RM ANOVA...
2. ### Statistical analysis - Work Delay - Some tests relations

Suppouse that we have a dataframe called dataWork with data from a database. There are several variables and 2 of them are: - Delay: time (minutes) to get to work (could be empty) - Nocturnal: 0 (work by day) 1 (work by night) we want to know the relation between delay and nocturnal. So...
3. ### What method is recommended, use contrast or t.test

I have a set with 60 observations, in four groups t1,t2,m1,m2 each with 15 observations. If I want to compare t1,t2 to m1,m2 or t1,m1 to t2,m2 what I did was to create a new variable so I can group the observations in 2 groups t and m and on the second iteration groups 1 and 2 then I just used a...
4. ### Automatic addition of contrasts

Hi, if I define contrasts for a factor variable with n levels, e.g. contrasts(x) <- c(-2,1,1) and I subsequently display these contrasts via contrasts(x) I obtain - beside the self-defined contrasts- (n-1) additional contrasts (second row): [,1] [,2] -2...
5. ### Confused with Contrasts

Hello, during the last days, I tried to understand the use of contrasts, but the more I read, the more I am confused. As far as I understand, a contrast represents a specific hypothesis regarding the relationship between means of K levels of a factor variable. This is done via...
6. ### puzzling results when contrasting conditions in 3 x 2 design

Hi everyone, I'm encountering something puzzling when analyzing my data. My data consists out of 2 independent variables and one dependent variables. When analyzing my data in a 3 (conditions: A, B, C) x 2 (Conditions: D, E) between subjects design, using Univariate Analysis of Variance in spss...
7. ### Performing oneway ANOVA with a linear monotonic contrast in SPSS from {n, mean, sd}

Does anyone know how I go about performing a oneway ANOVA with a linear monotonic contrast when I only have summary data for each group (i.e. n, mean, sd). I know how to do a standard oneway ANOVA in this situation: (see http://www-01.ibm.com/support/docview.wss?uid=swg21476127) But how...
8. ### how to do a contrast analysis for an interaction between two within subjects effects?

Hello! I have a quite simple data pattern but find it hard to test a specific contrast I expected. I have 2 within subjects factors, each with two levels. Let's call them reward (high vs. low) and task pressure (high vs. low), while the dependent variable is performance (see the example GLM...