Responses to the BASP psychologists’ p-value ban: the one that got away

When StatsLife collected responses to the BASP p-value ban (see blogs hither and yon), I suggested they contact Ian Hunt, a wise and philosophically minded critical voice in the wilderness of cookbook analysts. I also know that he and I take rather divergent opinions on deduction and induction and such, but I hold his arguments in the highest respect because they are carefully constructed. Alas! he couldn’t send in a response in time, but here it is, reproduced with his kind permission:

How good are the reasons given by the editors of Basic and Applied Social Psychology (BASP) to ban hypothesis tests and p-values?

I argue that BASPs reasoning for banning “statistical inference” is weak.

First, they (the editors) offer a non sequitur: ban p-values because “the state of the art remains uncertain” (2015 editorial) and “there exists no inferential statistical procedure that has elicited widespread agreement” (2014 editorial).  I argue inter-subjective (dis)agreement is not decisive.

Secondly, they imply that good inductive inferences require posterior probabilities. This is contentious, especially since both posteriors and p-values are just deductions.

Thirdly, they plead for larger sample sizes “because as the sample size increases, descriptive statistics become increasingly stable and sampling error is less of a problem.” This is contradictory: the evidence for this claim is best shown by the statistical inferences being banned.

Fourthly, they correctly assume that with a large enough sample size many “significant effects” (or “null rejections” or low p-values or interesting things or whatever) can be identified by looking at canny descriptive statistics and adroitly drawn charts. But I believe p-values ARE descriptive statistics – with which both frequentists and Bayesians can work.

Finally, BASP “welcomes the submission of null effects”.  But without tests and concomitant power profiles the evidential value of a “null effect” is unclear.

BASPs editors appear to conclude that modern statistics is inductive and akin to “the art of discovery” (as David Hand puts it). Fair enough. But I conclude that careful deductive inferences, in the form of hypothesis tests with clear premisses and verifiable mathematics, still have a role in discovering interesting things.

Now, it would be unfair of me to say anything more on this here but I believe you can hear Ian talking on this very subject at this year’s RSS conference, which is in Exeter. Personally, I’ve never been to Exeter, and I don’t think this is going to be the year for it either, but as Southern towns go, I suspect it’s neither as depressing as Weymouth nor as humourlessly overrated as Salisbury. (That counts as enthusiasm round here.) I recommend the conference to you. It’s just about optimal size and always interestingly diverse.

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