Statistics Snippets

Power for regression models

Power

Regression

R

Power simulation for regression starts with the question if one should draw the values for the predictors “inside” or “outside” of the power simulation. There is a reason…

Nora Wickelmaier

A volleyball example of differentiation and integration

Probability

In the lecture on probability theory, I’m often in need of a basic example of the derivative, the integral, and their relationship. So here it is.

Florian Wickelmaier

Power for designs with two or more measurement points

Mixed-effects models

Power

R

A few weeks ago, we met to talk about a power analysis for my pre/post study. Now, I want to add a second delayed post-test assessment one week later. Does this change my…

Nora Wickelmaier

Internal meta-analysis - why, when and how?

Meta-analysis

R

I want to report an aggregated effect size over several of my studies. Should I use a meta-analysis for that or is there a better way?

Nora Wickelmaier

Conditional testing when normality assumption is violated

Categorical predictors

Power

R

In the era of preregistration and after the replication crisis in psychology (and, of course, other disciplines), I am inclined to use the sentence “No analysis decisions…

Nora Wickelmaier

Testing a group effect when sub-groups are present

Mixed-effects models

R

Power

Should I use a mixed model, wenn I have subgroups in my between groups?

Nora Wickelmaier

Minimum requirements for reproducible R scripts

Data management

R

Reproducibility

This is a collection of some simple steps to create an R script that you can share with others. The tips provided here will not make your analysis reproducible in a strict…

Nora Wickelmaier

Effects vs. dummy coding

Categorical predictors

R

Let us look at the differences between effects and dummy coding for regression models with categorical predictors.

Nora Wickelmaier

Understanding categorical predictors in a mixed-effects model

Categorical predictors

Mixed-effects models

R

This post is meant to give you a better understanding how to interpret parameters for categorical predictors in a mixed-effects model. Understanding what the parameters mean…

Nora Wickelmaier