• Number of diseased trees
  • Number of salamander eggs that hatch
  • Number of crimes committed in a neighborhood

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Why Mixed Models are Harder in Repeated Measures Designs: G-Side and R-Side Modeling

I have recently worked with two clients who were running generalized linear mixed models in SPSS. Both had repeated measures experiments with a binary outcome. The details of the designs were quite different, of course. But both had pretty complicated combinations of within-subjects factors…

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Get your Sampling Out of My Survey Errors…

These types of errors are not associated with sample-to-sample variability but to sources like selection biases, frame coverage issues, and measurement errors. These are not the kind of errors you want in your survey.

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Target Population and Sampling Frame in Survey Sampling

As it is in history, literature, criminology and many other areas, context is important in statistics. Knowing from where your data comes gives clues about what you can do with that data and what inferences you can make from it. In survey samples context is critical because it informs you about how the sample was selected and from what population it was selected…

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Sampling Error in Surveys

What do you do when you hear the word error? Do you think you made a mistake? Well in survey statistics, error could imply that things are as they should be. That might be the best news yet–error could mean that things are as they should be. Let’s break this down a bit more before you think this might be a typo or even worse, an error…

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February 2015 Membership Webinar: Probability Rules and Concepts: A Review

Do you remember all those probability rules you learned (or didn’t) in intro stats? You know, things like the P(A|B)?

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Specifying Variables as Within-Subjects Factors in Repeated Measures

I want to do a GLM (repeated measures ANOVA) with the valence of some actions of my test-subjects (valence = desirability of actions) as a within-subject factor. My subjects have to rate a number of actions/behaviours in a pre-set list of 20 actions from ‘very likely to do’ to ‘will never do this’ on a scale from 1 to 7,..

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Interpreting Interactions when Main Effects are Not Significant

If you have significant a significant interaction effect and non-significant main effects, would you interpret the interaction effect?

It’s a question I get pretty often, and it’s a more straightforward answer than most.

There is really only one situation possible in which an interaction is significant, but the main effects are not: a cross-over interaction.

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R Graphics: Plotting in Color with qplot Part 2

In the last lesson we saw how to use qplot to map symbol colour to a categorical variable. Now we see how to control symbol colours and create legend titles..

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R Graphics: Plotting in Color with qplot

In this lesson, let’s see how to use qplot to map symbol colour to a categorical variable. .

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