Number of siblings vs. total fertility rate

This is commentary on: Ellis, L., Hoskin, A. W., Dutton, E., & Nyborg, H. The Future of Secularism: a Biologically Informed Theory Supplemented with Cross-Cultural Evidence. Evolutionary Psychological Science, 1-19. For over a century, social scientists have predicted declines in religious beliefs and their replacement with more scientific/naturalistic outlooks, a prediction known as the secularization…

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Did Turkheimer et al (2003) replicate?

Lots of published psychology studies don’t replicate well, in particular cute things like interactions, counter-intuitive or priming effects. In general, traditional behavioral genetics studies have replicated well. This is not surprising because basically the same method (ACE fitting) has been applied to lots of large datasets, and studies that use consistent methods on large datasets…

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R functions for analyzing missing data

I’m reading Missing Data: A Gentle Introduction and it mentions various methods to understand how data are missing in a given dataset. The book, however, is light on actual tools. So, since I have already implemented a few functions in my package for handling missing data, I decided to implement a few more. These have…

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Estimation of piecewise linear functions

Suppose you have some dataset where you know or suspect that the real generating function is actually a piecewise function with k pieces each of which is a standard linear model. How does you find these? This is the problem presented to me from a friend. I came up with this method: Find all the…

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A more intuitive explanation of the correlation

Someone asks on Reddit: Can someone intuitively explain the correlation formula? I know what the Cov(X,Y) means. It tells you if the relationship between the variables X and Y is positive or negative (although I must admit I dont really know what the actual number means, I only look the the sign). I know what…

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Correcting for n-level discretization?

When one has a continuous variable and then cuts it into bins (discretization) and correlates it with some other variable, the observed correlation is biased downwards to some extent. The extent depends on the cut-off value(s) used and the number of bins. Normally, one would use polychoric-type methods (better called latent correlation estimation methods) to…

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Causality, transitivity and correlation

Disclaimer: Some not too structured thoughts. It’s commonly said that correlation does not imply causation. That is true (see Gwern’s analysis), but does causation imply correlation? Specifically, if “→” means causes and “~~” means correlates with, does X→Y imply X~~Y? It may seem obvious that the answer is yes, but it is not so clear….

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