February 3, 2016

Units matter

I think this is just a typo in the Herald story about testing for methamphetamine in state houses:

Forensic scientist Dr Nick Powell said any meth contamination above 0.5mcg per 100sq m of surface risked headaches, coughs and sleeplessness, and poorer appetite and infant brain growth.

The NZ standard for cleanups is 0.5μg per 100cm2, which is designed to be safe, rather than just on the borderline of danger, so even with square centimetres this is a strong claim. Changing the denominator to square metres makes the claim ten thousand times stronger.

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Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »