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1. comparing test results obtained on the basis of different sample sizes

I have variables a1 and a2 with 57 observations each, and variables b1 and b2 with 29 observations each. I compare a1 with a2 by means of a paired-samples t-test, this gives p<0.001. Next, I compare b1 with b2 by means of a paired-samples t-test, this gives p>0.05 (actually p>0.10). I compared...
2. mixed-effects models with (g)lmer in R and model selection

Mixed-effects models are wonderful for analyzing data, but it is always a hassle to find the best model, i.e. the model with the lowest AIC, especially when the number of predictor variables is large. Presently when trying to find the right model, I perform the following steps: 1) Start...
3. pairwise comparisons in GLM

Hello, I'm doing pairwise comparisons (Bonferroni) in GLM using SPSS. One (probably stupid) question: are the p values one-sided or two-sided? If they are two-sided, how do I get one-sided p-values? Thanks, Wilbert
4. MANOVA / testing multivariatie normality

Hi all, I'm doing an MANOVA with two dependent variables and one fixed factor (three levels). It is said that I need to test for multivariate normality. What is the right way to test for multivariate normality in SPSS? Do I need to test per level or all levels together? best regards Wilbert
5. (adjusted)R-squared / eta-squared / omage-squared for ANOVA

Dear all, When obtaining ANOVA results with SPSS we also get a R-squared and an adjusted R-squared. For a multi-way ANOVA the eta-squared is given per factor or interaction. The measures are criticized by - among others - Andy Field: "However, this measure of effect size is slightly...