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1/10 So hey! Here’s my next installment of “School Safety B.S. Explained”. Happily for us all, this one’s shorter than the last, and it’s also wicked important given Baker’s absurd revamp last week of COVID metrics & their implications re: reopening BPS buildings. #SafetyFirstBPS
2/10 Baker announced changes to the "stoplight" metric, and cited studies “proving” safety of in-person instruction almost everywhere. @TracyNovick just wrote an awesome thread re: the problems w/ those studies & @47Sasaki has written extensively about the incidence metric...
3/10...and I’ll link to both in comments. I want to talk about the positivity rate part ‘cause I think it’s even worse than it looks. See how red now depends on 10+ cases/100k AND pos. rate of >4%? You’d think that’d be the same 4% that (ha!) was in the BPS/BTU MOU, right? But...
4/10 ...LOL no. This is a Mass DPH metric, and they use a vastly different calculation of pos. rate than BPHC. DPH’s method is “positives per # of tests”, while BPHC’s is “positives per people tested”. (Bear with me through this part, please - it’s super important. Also, charts!)
5/10 Say you’ve got a group of 100 people. They all get tested for Coronavirus on Monday, and 2 are positive. The remaining 98 get tested on Tuesday, and 3 of them are positive. Remaining 95 get tested on Wednesday, and 6 of them are positive. That’s 11 positives in three days.
6/10 “Positives per person” says ok, 11 total positives out of 100 people: that’s a positivity rate of 11%.
“Positives per tests” takes exact same data but says ok, 11 positives out of 293 (100+98+96) tests: that’s a pos. rate of 3.8%.
Here’s what this looks like in real life:
“Positives per tests” takes exact same data but says ok, 11 positives out of 293 (100+98+96) tests: that’s a pos. rate of 3.8%.
Here’s what this looks like in real life:
7/10 This means that in a place where the same asymptomatic ppl are frequently tested (college kids in dorms, HCW), it’s virtually impossible for that rate to rise anywhere NEAR 4%. Per that chart, on 10/30 the “per people” rate in MA was 6.5%. “Per test” rate for SAME DAY: 1.9%.
8/10 If that is indeed the metric they’re using - and please, anyone, tell me if you think I’ve got this wrong - Boston, realistically, will NEVER be in the red zone. And right now DESE’s saying any city/town not in red needs to be in-person full time.
9/10 Final bit of b.s.: Mass DPH used to provide both numbers if you cared enough to dig for them. But as of this week, they are no longer even REPORTING the “per people” number - that top line will just be...gone. (I’d love to hear the justification for that.) So...
10/10 … @BTU66, please get clarity re: which method DESE is talking about with their 4%. And if it IS per-test, then WTF with the next-level sketchiness of making it look like the exact same # as MOU?! And if it’s not, lemme know and l’ll JOYFULLY post a retraction. Be safe, all.
