So, The Big Mask study has been published, and I thought rather than expound on what the results DID show (everyone's doing that), I might point out a few things that they DIDN'T show 1/npic.twitter.com/zG4jtXQVVq
You can add location information to your Tweets, such as your city or precise location, from the web and via third-party applications. You always have the option to delete your Tweet location history. Learn more
12/n Again, this is not a minor point - masks may indeed not reduce infection numbers much during lockdown, but that doesn't say a lot about their effectiveness at other times
13/n Ok, a technical addition that is nevertheless important. The authors do not report correcting their result for the test sensitivity and specificity of their serology test
14/n Serology tests are used to find antibodies, and they are (as all tests are) imperfect So, usually we correct for the imperfections to get a better estimate of the true number of people with antibodies
15/n In this case, the study found that 1.8% of people in the mask group had antibodies, compared to 2.1% of people in the non-mask group But those are just the RAW figurespic.twitter.com/NtiZuV9Uml
16/n If we use the Rogen-Gladen estimator, which is a pretty standard correction for test characteristics, we see instead that 1.59% and 1.95% of people in masks/no masks were probably infected, respectivelypic.twitter.com/d4rPZ5kJVw
17/n This sounds like a minor point, but it actually isn't - if only 1.59%/1.95% of people were infected, it means that the study was underpowered for its main analysis, and thus we can't conclude much from the results
18/n Sorry, small correction - I used the final totals of 1.8% and 2.1% not the actual antibody numbers of 1.6% and 1.7% in that calculation. If you apply the correction properly, you get 1.56% masks and 2.09% non-masks
19/n For some context, to find a difference this small, the study would've needed to recruit about 24,000 people, or 12,000 in each group, which is about 4x as big
I'd also not that mask/no-mask was for lower risk social settings, not for higher risk work settings.
Not even sure that you can say that because surgical mask protect the other people not the wearer they didn't isolate these people from greater society nor test the people the participants came in contact with. All this showed was surgical mask on a wearer doesn't protect the wea
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.