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Think about total N, not n per cell
The bottom line of this post is simple. There are lots of rules of thumb out there for minimum sample sizes to use in between-subjects factorial experiments. But they are virtually always formulated in...
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Follow-up: What about Uri’s 2n rule?
This post is a quick follow-up to yesterday’s post on sample size rules. Basically I thought it was a little too long to go in the comments section so here it is. Some people on twitter (and in my blog...
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Don’t fight the power (analysis)
Public Enemy are famously skeptical of power analysis. Researchers often feel uneasy about using power analysis to design their actual experiments because of uncertainty about the effect size in the...
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Five different “Cohen’s d” statistics for within-subject designs
Jeff Rouder poses an “effect size puzzler” where the puzzle is simply to compute a standardized effect size for a simulated dataset where subjects make 50 responses in each of 2 conditions. He offers a...
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Designing multi-lab replication projects: Number of labs matters more than...
In a multi-lab replication project, multiple teams of investigators team up to all run the same study (or studies) concurrently at different research sites. The best examples of this in psychology are...
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Using causal graphs to understand missingness and how to deal with it
If you’re reading this, you probably know that missing data can cause a lot of problems in a data analysis, from reduced efficiency at best to seriously mistaken conclusions at worst. You may even be...
View ArticleReading list: Introduction to linear mixed models for cognitive scientists
(Note: This is one of three posts that I wrote some time ago that have just been languishing under the “Misc.” tab of my website for a while, because for whatever reason I didn’t feel that they were a...
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What is the yearly risk of another Harvey-level flood in Houston?
You’ve likely heard that the flooding in Houston following Hurricane Harvey is reportedly a 500-year or even 1000-year flood event. You’ve perhaps also heard that this is the third 500-year flood that...
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The hierarchical ordering principle
(Background reading: Jeff Rouder’s blog post on the “dominance principle”, which this post is mainly a response to.) How many subjects should we routinely aim to recruit when we conduct experiments...
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Logistic regression is not fucked
Summary: Arguments against the use of logistic regression due to problems with “unobserved heterogeneity” proceed from two distinct sets of premises. The first argument points out that if the binary...
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