4 ms·

The description of S15 gives a plausible explanation of why the effect is much less for some of these city than for Jena. Of course this is speculation but this

by klmr 6y ago

The description of S15 gives a plausible explanation of why the effect is much less for some of these city than for Jena. Of course this is speculation but this doesn’t mean that fig S15 disproves the paper’s finding. And for Jena the effect is extraordinarily strong, and well controlled for. I’m not aware of any alternative explanation (to mask-wearing) which could explain this effect, and until I hear such an explanation I consider this strong evidence for the effect of mask-wearing on COVID-19 transmission. This study isn’t the only evidence for the effectiveness of mask-wearing but it’s certainly part of the overall evidence, and I’d like to hear better arguments for calling it “bad”.

lixtra 6y ago
I found someone on the internet who said they prayed for Weimar, a smaller neighbor city of Jena. Luckily you can use the same mechanics of the study to grasp the effects of their prayer. It worked similarly well[1] as masks in Jena[2]. Jena is a single data point supporting the effectivity of masks (there could be indirect effects at work as well, i.e. people better grasping the severity of the situation). The sophisticated average that they use as comparison makes it appear to carry more confidence than it does. [1] https://www.corona-in-zahlen.de/landkreise/sk%20weimar/ https://www.corona-in-zahlen.de/landkreise/sk%20weimar/ [2] https://www.corona-in-zahlen.de/landkreise/sk%20jena/ https://www.corona-in-zahlen.de/landkreise/sk%20jena/
- klmr 6y ago
  > I found someone on the internet who said they prayed for Weimar, a smaller neighbor city of Jena. And that is why post-hoc hypotheses aren’t valid. It does not, however, invalidate this study. Incidentally, I found somebody who prayed for all cities except Weimar and Jena, so this neutralises your anonymous friend’s prayer.
  - lixtra 6y ago
    > And that is why post-hoc hypotheses aren’t valid. I agree on this. Can you point to where they announced the study on April 6th or before? Or did the decide to look at Jena only after the data was available? How is that not a post-hoc hypothesis? Of course, both general hypotheses of masks and prayer predate Covid19. > It does not, however, invalidate this study. No. The study contributes a single data point in favor of masks, but is not very convincing (in that the authors did not look deep into contradictions and alternative explanations) and of course not conclusive as the bad title makes it appear.
    - klmr 6y ago
      The study was designed to tease out mask-wearing by attempting to control for other factors via its study design. — They did this specifically by comparing a mask-wearing city with a synthetic control unit based on reference populations without mask-wearing rules. So the hypothesis “mask-wearing helps” is, by design, not post-hoc. You’re right that it’s a single data point (though with a strong effect size). And, being an observational study, it simply can’t exclude all confounding factors, and will never approach the strength that a controlled study could. Nobody is disputing that. Interpretation of observational studies always needs to be tempered by the reality that it’s impossible to control for all confounders. But within these given constraints the study essentially provides as strong evidence as could reasonably be expected (unless the study has a flaw that I’m overlooking and which, as far as I know, hasn’t yet been pointed out elsewhere). Their design of the synthetic control is statistically sound and controls for a very large number of reasonable confounders. And, contrary to the claim in the comment I’m replying to, data from other cities does not invalidate the study’s findings. As far as I can see, the study’s inadequacies are all due to external circumstances and not because it’s a bad study.

by klmr 6y ago

lixtra 6y ago

I found someone on the internet who said they prayed for Weimar, a smaller neighbor city of Jena. Luckily you can use the same mechanics of the study to grasp the effects of their prayer. It worked similarly well[1] as masks in Jena[2]. Jena is a single data point supporting the effectivity of masks (there could be indirect effects at work as well, i.e. people better grasping the severity of the situation). The sophisticated average that they use as comparison makes it appear to carry more confidence than it does. [1] https://www.corona-in-zahlen.de/landkreise/sk%20weimar/ https://www.corona-in-zahlen.de/landkreise/sk%20weimar/ [2] https://www.corona-in-zahlen.de/landkreise/sk%20jena/ https://www.corona-in-zahlen.de/landkreise/sk%20jena/

klmr 6y ago
> I found someone on the internet who said they prayed for Weimar, a smaller neighbor city of Jena. And that is why post-hoc hypotheses aren’t valid. It does not, however, invalidate this study. Incidentally, I found somebody who prayed for all cities except Weimar and Jena, so this neutralises your anonymous friend’s prayer.
- lixtra 6y ago
  > And that is why post-hoc hypotheses aren’t valid. I agree on this. Can you point to where they announced the study on April 6th or before? Or did the decide to look at Jena only after the data was available? How is that not a post-hoc hypothesis? Of course, both general hypotheses of masks and prayer predate Covid19. > It does not, however, invalidate this study. No. The study contributes a single data point in favor of masks, but is not very convincing (in that the authors did not look deep into contradictions and alternative explanations) and of course not conclusive as the bad title makes it appear.
  - klmr 6y ago
    The study was designed to tease out mask-wearing by attempting to control for other factors via its study design. — They did this specifically by comparing a mask-wearing city with a synthetic control unit based on reference populations without mask-wearing rules. So the hypothesis “mask-wearing helps” is, by design, not post-hoc. You’re right that it’s a single data point (though with a strong effect size). And, being an observational study, it simply can’t exclude all confounding factors, and will never approach the strength that a controlled study could. Nobody is disputing that. Interpretation of observational studies always needs to be tempered by the reality that it’s impossible to control for all confounders. But within these given constraints the study essentially provides as strong evidence as could reasonably be expected (unless the study has a flaw that I’m overlooking and which, as far as I know, hasn’t yet been pointed out elsewhere). Their design of the synthetic control is statistically sound and controls for a very large number of reasonable confounders. And, contrary to the claim in the comment I’m replying to, data from other cities does not invalidate the study’s findings. As far as I can see, the study’s inadequacies are all due to external circumstances and not because it’s a bad study.