Substantive relevance — not ‘clever’ design — is what matters most in science

11 Jun, 2019 at 16:40 | Posted in Statistics & Econometrics | 1 Comment


If anything, Snow’s path-breaking research underlines how important it is not to equate science with statistical calculation. And that the value of ‘as-if’ random interventions and experiments ultimately depend on the degree to which they if shed light on substantive and interesting scientific questions.

All science entail human judgement, and using statistical models doesn’t relieve us of that necessity. And we should never forget that the underlying parameters we use when performing statistical tests are model constructions. And if the model is wrong, the value of our calculations is nil. As ‘shoe-leather researcher’ David Freedman wrote in Statistical Models and Causal Inference:

I believe model validation to be a central issue. Of course, many of my colleagues will be found to disagree. For them, fitting models to data, computing standard errors, and performing significance tests is “informative,” even though the basic statistical assumptions (linearity, independence of errors, etc.) cannot be validated. This position seems indefensible, nor are the consequences trivial. Perhaps it is time to reconsider.

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  1. The leading competing hypotheses of the time came from the miasmic theory, the idea that cholera was a multifactorial disease particularly associated with “bad air” of which there was plenty in early industrial London. William Farr, an accomplished statistician, produced evidence showing an inverse correlation with topographical elevation around the same time Snow’s evidence concerning the competing water companies was circulated.
    It was only in 1866 while studying another outbreak, where infection was traced to a particular reservoir that Farr was led to concede the superiority of Snow’s explanation.
    Ultimately, it was the discoveries of microbiology, which confirmed a mechanism in the germ theory that made Snow’s guess credible, a guess that he himself became convinced of from his experience in investigating the Broad Street pump.

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