March 2, 2021

Briefly

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  • About 140% of Kiwis aged 20-24 are on Facebook (NZ$ Herald) — more precisely, that’s the ratio of Facebook’s claimed “reach” to StatsNZ’s population estimates.  This is an age group where the census does relatively badly, but nowhere near that badly.
  • The false-positive rate of the PCR tests for Covid has become topical again, so it’s worth revisiting how we know it is very low. In addition to knowing it should be low based on how the test works, we have simple, direct evidence that the false positive rate is low for the test as used in NZ. We have so far performed 1,720,909 tests in New Zealand and 1,717,865 of them, or 99.8%, have been negative. The 0.2% left over include all the true positives (including people with serious Covid cases), all the inconclusive results, and any false positives.
  • Business$ Week reports on the countries of origin of Covid cases in MIQ.  As you’d expect, the top four are four of the top five in the world for Covid cases: US, India, UK, Russia. Brazil, the other country in the top five, doesn’t show up, but we don’t get as many immigrants or visitors from South America.  Also, as you’d expect, China is very low on the list, because we didn’t start the MIQ system until after they’d controlled their big outbreak. Image (from tweet by @victoriayoung03)
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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 »