Andres Gelman rebuts Bem’s ESP paper

Thanks to my friend and fellow Ph.D. candidate Lee Becker, I have an update on my earlier post regarding Daryl Bem’s ESP paper.

On his blog, Columbia University statistician Andrew Gelman writes:

All the statistical sophistication in the world won’t help you if you’re studying a null effect. This is not to say that the actual effect is zero–who am I to say?–just that the comments about the high-quality statistics in the article don’t say much to me…

As David Weakiem and I have discussed, classical statistical methods that work reasonably well when studying moderate or large effects (see the work of Fisher, Snedecor, Cochran, etc.) fall apart in the presence of small effects.

I think it’s naive when people implicitly assume that the study’s claims are correct, or the study’s statistical methods are weak. Generally, the smaller the effects you’re studying, the better the statistics you need. ESP is a field of small effects and so ESP researchers use high-quality statistics.

To put it another way: whatever methodological errors happen to be in the paper in question, probably occur in lots of researcher papers in “legitimate” psychology research. The difference is that when you’re studying a large, robust phenomenon, little statistical errors won’t be so damaging as in a study of a fragile, possibly zero effect.


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