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Pediatric COVID-19 Cases in Counties...

2) Take, e.g., cdc.gov/mmwr/volumes/7. There are two big problems with how this study is presented.

cdc.gov

This report describes pediatric COVID-19 cases in counties with and without school mask requirements.

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3) First, the highlight is that mask mandates decreased COVID in schools, P<0.001. Which, sure, it would be pretty weird if they didn't decrease COVID *at all*. But--everything's a tradeoff. How much impact do they have?

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4) Well, there's not much discussion of that! Because the core focus is that there's a *statistically significant* result, rather than how *important* that result is. That's stupid. The more important question is how large the effect is, not how large the study was!

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5) In this case, it seems like the mandates decreased COVID in schools by ~20 cases per 100,000 children per week. That's ~0.02%/week, or ~1%/year. Would you rather: a) wear a mask for 100 years b) get COVID once I'll let you judge how the benefits compare to the costs.

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Absolute % change in COVID risk seems misleading for what this study is evaluating. Masks *did* have a large impact relative to the increased COVID risk at school, cutting the increase by 50%+. The reason the absolute change was so small is the % is so small to begin with: ~0.04%

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but that matters! The tradeoff here is "days in mask" vs "cases of COVID".

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Oh I totally agree it matters! But it matters as a matter of policy context, not really this study in particular. The study does suggest masks in school work and have a large effect. Whether the underlying problem is even big enough to be worth the effort is a separate question