Effect size statistics are expected by many journal editors these days.

If you’re running an ANOVA, t-test, or linear regression model, it’s pretty straightforward which ones to report. 

Things get trickier, though, once you venture into other types of models. [click to continue…]

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What is a Logit Function and Why Use Logistic Regression?

One of the big assumptions of linear models is that the residuals are normally distributed. This doesn’t mean that Y, the response variable, has to also be normally distributed, but it does have to be continuous, unbounded and measured on an interval or ratio scale.

Unfortunately, categorical response variables are none of these.

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May 2015 Membership Webinar: Transformations & Nonlinear Effects in Linear Models

Why is it we can model non-linear effects in linear regression? What the heck does it mean for a model to be “linear in the parameters?”

In this webinar we will explore a number of ways of using a linear regression to model a non-linear effect between X and Y.

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Linear Models in R: Improving Our Regression Model

Last time we created two variables and used the lm() command to perform a least squares regression on them, and diagnosing our regression using the plot() command..

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Linear Models in R: Diagnosing Our Regression Model

Last time we created two variables and used the lm() command to perform a least squares regression on them, treating one of them as the dependent variable and the other as the independent variable. Here they are again..

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Linear Models in R: Plotting Regression Lines

Today let’s re-create two variables and see how to plot them and include a regression line. We take height to be a variable that describes the heights (in cm) of ten people.

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Models for Repeated Measures Continuous, Categorical, and Count Data

Lately, I’ve gotten a lot of questions about learning how to run models for repeated measures data that isn’t continuous. Mostly categorical. But once in a while discrete counts. A typical study is in linguistics or psychology where..

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April 2015 Membership Webinar: Confidence Intervals

In this webinar we’ll clear up the ambiguity as to what exactly is a confidence interval and how to interpret them in a table and graph format..

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3 Tips for Keeping Track of Data Files in a Large Data Analysis

If you’ve ever worked on a large data analysis project, you know that just keeping track of everything is a battle in itself. Every data analysis project is unique, but here are a few strategies I used in a recent project that you may find helpful. They didn’t make the project easy, but they helped keep it from spiraling into overwhelm…

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Preparing Data for Analysis is (more than) Half the Battle

Just last week, a colleague mentioned that while he does a lot of study design these days, he no longer does much data analysis. His main reason was that 80% of the work in data analysis is preparing the data for analysis. Data preparation is s-l-o-w and he found that few colleagues and clients understood this…

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