1/ What does this mean for research? For example, while my twitter followed has increased absurdly since early last year because of my work on data analysis on SARS-Cov-2, I was mostly known for my work in performance analysis.
2/ What performance analysis teaches you is that you run experiments of the type 'If P then Q' every single day, several times a day.
For ex. "If I change this data structure then I will be able to obtain better performance by accessing memory contiguously"
3/ Now, when you enter into the realm of 'how the physical CPU is working' then becomes far more difficult. The reason behind that is that with that many moving parts noise is very difficult to separate from the signal.
4/ That's where Modus Tollendo Tollens comes to the rescue. Because now instead of trying to prove "If P then Q" most of the time proving "not Q" proves to be easier. When designing the @ravendb Storage Engine, most of the time was spent on proving "not Q".
5/ But the most interesting and overlooked use of that is that: If we though that P was the caused of Q. If we could find an instance where not Q, we immediately knew P (while related) is not the actual reason why Q happens. Therefore, we need to think and refine the hypothesis.
6/ That has immediate impact in how @LDjaparidze and me tackle our research. There are always million of competing hypothesis (we even have different ideas on certain topics) but our discussions revolve around "proving not Q" to rule out hypothesis.
7/ Overlooking the capability of Modus Tollendo Tollens to rule out hypothesis has lead several SARS-Cov-2 researchers into rabbit holes that is very difficult then to get out from.
8/ When analyzing data, this is probably the most effective and powerful method. And something that most are not using.

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More from @federicolois

7 Feb
1/ Let's look at this paper: "Influenza Virus Aerosols in the Air and Their Infectiousness" from 2014 (we cannot claim this was unknown). We know now that we have a new kid on the block now, ready to challenge Influenza for supremacy in the transmissibility metric.
2/ So there were these guys that actually infected people with Influenza to measure how infectious it was. That is a 'challenge study', this is no 'model' this is actual humans. And they found, that with as much as 3000 copies you get it.
3/ Another study actually measured how many particles an adult would inhale in 1 hour given the concentrations found on a health center, a day-care center, and airplanes.
Read 19 tweets
6 Feb
1/ I was sent this paper. You know I have disregard it before because the filtering mechanic was really not significative for the type of airflow conditions imposed by masks. How wrong I was on not looking deeper.
2/ I have been told by @Kevin_McKernan that you always have to look for "Where is Waldo?" in this type of studies. The first interesting fact comes from Table 1. Each experiment has different experimental setups, that is good enough to disqualify in my book.
3/ But then I skipped to Table 4. Mind you, almost none were statistically significative. But remember Table 1. So you see a correlation there?
Read 6 tweets
6 Feb
1/ I went for ice cream. The cashier asked me to put my face mask on. I said: "Fine. I evaluated the evidence myself and it's bad. If you want the safety theater, let's do it (taking my facemask out of my dirty pocket), BUT, first I have to insist for you to use yours properly".
2/ This is what people don't get. You are in the shop, you take it out when no other people are around. If they were infected, BANG, there are virions everywhere floating around anyways. Safety, yeah right.
3/ So if an actual vulnerable (who thinks his nifty masks would protect him) arrives, he will inhale all those virions AND also some of them go straight to the outer layer. If it is a cloth one, then he is undoubtedly gonna inhale aerosolized virus over time.
Read 13 tweets
4 Feb
1/ This is what many forget, if you say something is wrong you have the higher ground. Find a counterexample, it's the easiest thing to do. Though many fail in such an easy endevour and claim misinformation. Don't be like that, provide evidence (counterexample) for your claims.
2/ I am not saying this lightly. I have received many: "that claim is absurd" from epidemiologists, MDs and health professionals about the claims on our papers. But when we asked for the evidence.
3/ come on its easy, find a counterexample. I tend to do that a lot on discussions, after claim X my response is always explain to me Y contradicts that claim. A working theory to claim evidence status must explain the corner cases. You start there, not on the easy stuff.
Read 6 tweets
31 Jan
1/ Very good thread about all the things that most modelers fail at, which is predicting outcome. As shown your assumptions are everything. For example, our model only estimate immunity through simplified cohort dynamics. Its good for that, it just happen it is also very useful.
2/ Language is a model that is useful to communicate ideas. In the same way as language, models shape reality. If your model simplifies an specific aspect, your reality also becomes less rich. You always have to be careful what model you accept as correct and why.
3/ but the most important realization you have to develop is that models are useful, until they arent. The more disconnected from reality, the more effects you are explaining without fully understanding them.
Read 10 tweets
31 Jan
Yes they should. Dexamethasone, Bromhexine, Melatonine and a few others like Colchine had in-silico interesting results as early as 1st of March. With the exception of dexa still waiting for the large scale RCTs.
Haven't said this publicly before but early on with a group of MDs, biotech and others researchers we built a protocol coupling statistical exploration techniques from AI with low toxicity drugs for profilaxis use. Apparently it was too innovative and rejected by our government.
With the exception of dexamethasone, all the others were already identified to be used in the early treatment of at risk with high probability contract protocol. Probably ivermectin that appeared later would have made the cut too, given the profile.
Read 9 tweets

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