Post #1010: William and Mary and the power of big round numbers.

Posted on February 15, 2021

Source:  William and Mary COVID-19 dashboard, updated to COB 2/15/2021.

I pulled up the William and Mary COVID-19 dashboard this afternoon and my heart skipped a beat.  I immediately read this as saying that THEY’VE HAD A HUNDRED CASES OF COVID-19 ON CAMPUS!  It took me a minute to realize that what it actually says is that they’ve had a hundred cases of COVID-19 on campus.

That big round number is a real kick in the head.  And of course, I had mis-remembered what the reading was from last Friday.  Which is completely unhelpful when you’re just primed to panic.

Anyway, for those of you who are keeping score, here’s the update from my last post on this.  This time I’m reproducing the full spreadsheet.  (Not that anybody will check the methods, but it just looks a lot more science-y that way.)

This has a lot of extraneous information.  The only columns that matter on the table below are highlighted in yellow.

Between my last posting and this one, we’d have expected W&M to add 15 cases, based on average incidence in Virginia.  They only added 11.  So they actually improved, relative to the Virginia average for that age group.

Fact is, just as was true last semester, William and Mary is starting off with a count of on-campus COVID-19 positives that is very close to the rate you would expect, based on incidence in the community (for 21-30 year olds).  And they are slowly bringing that down somewhat below would you would expect for the community rate. ‘

Here’s how the comparison of actual and expected cases looked last year, in early November of 2020.



If anything, this year W&M is ahead of the game, compared to last semester, with the observed campus rate now about 10% below the Virginia 21-30 year old community rate.  Which makes sense to me, because last year they started the semester pulling some students off campus for holding illegal parties.  This year, one way or the the other, the students seem to have wised up.  (Either they’re not having those non-socially-distanced events, or they’ve gotten smarter about keeping them under wraps.)

If there is a lesson here, it’s not to be fooled by round numbers.  And not to let your heart do your data interpretation, particularly when faced with a big fat round numbers.

And heed the Mythbusters’ advice: