@spazzpp2 but it doesnt change how we analyze the contribution of any factor. so the reason current studies are invalidated remains true regardless of the R0 value.

@freemo
I don't get it. If not wearing a mask is an option, then you need to compare this (pure R0) with wearing a mask (R0 * Pmask + Rmask) where Pmask is the probability/factor of stopping infection and Rmask is the rate of getting sick by wearing a mask; or sth like that.

However if R0 >> Rmask, the consideration of Rmask is meaningless.

@freemo Now, your point was, that Rmask > R0?

@spazzpp2 yes but you;d have to do so in a controlled setting where you know the **only** factor that is different is the mask. That would mean intentionally exposing a group to the virus which is unethical and thus impossible.

Any attempt to do the experiment using observational data, and thus other variables are not controlled would lead to the post hoc ergo propter hoc fallacy i mentioned.

So in effect there is no way to actually test the hypothesis and thus the problem.

@freemo What about
R_0*P_mask + R_mask ~= R_0*P_avoidance + R_avoidance
=>
R_0 = (Rm-Ra)/(Pm-Pa) etc.?

@freemo I think R_0 is being reconstructed using actual interviews.

@spazzpp2 exactly, thus the problem. Interviewd people are "observational data" and their choices are not controlled. Thus the studies are victim to the fallacy mentioned

@freemo
I mean investigation

@spazzpp2 In what way is it not observational? The problem here is your drawing inference from things happening in the wild where wearing a mask is a choice

@freemo
If more people get sick because they didn't wear a mask (observed or honestly) than people that did (observed or dishonestly), wearing a mask in the wild is at least as good. If the opposite would be the case, wearing a mask is at least as bad as observed.

@spazzpp2 you are missing the point. If people in a study are wearing a mask because the choose to do so then you cant be sure if the mask is the thing effecting the transmission of the disease or if it is something else that mask wearers are likely to do non-mask wearers dont.

For example say people who take the virus seriously are the people who wear masks, they are also the people who wash their hands frequently. That means people who wear masks are likely to be the people washing their hands. So even if masks have no effect but hand washing does then you would observe people who wear masks get sick less even though the masks arent the reason.

@freemo
But how can you use that as an argument against mask while masks are intuitively (and experimentally) well working spread resistors?

@spazzpp2
I would argue that they dont work intuitively and that my interpritation is the intuitive one. They also arent working experimentally as i already covered why the experiments out there are bogus.

So when there is no experimental data to prove a conclusion either way i fall back on intuition and common sense, which tells me masks are spreading disease.

@freemo
well thats one possible opinion

@spazzpp2 Yes it is, and due to the lack of good or definitive studies all we have to go on is opinion. Thats my point.

@freemo
I should go search for studies now.

@spazzpp2 indeed but it is important to understand how to interprit studies and to identify direct evidence and confounding so you can get a sense of if causality is demonstrated.

The problem with lay people reading studies is they cant really do the work, they can just read the conclusions and have no idea as to how strongly those conclusions represent causality

@freemo
feels like you're overgeneralizing

@spazzpp2
In what sense? The problems with observational data and confounding is a fundamental component of data science.

@freemo
You need to prove that mask usage in practice increases diseases. that is pretty simple to do, isn't it?
E.g. give humans/animals used masks and observe, etc.

@spazzpp2
In theory it would be easy in a lab setting, yes. The reason we cant and wont do it is ethics, you cant expose people go a deadly disease intentionally.

@freemo
do you know it's deadly?
I think, they already studied masks after several uses in microbiological labs.

@spazzpp2 yea we know COVID kills

The existance of studies doesnt imply the studies support the conclusions your drawing. As I covered wgle studies do exist none of them are valid or complete for the aforementioned reasons.