Thanks for the explanation. I do not understand the formula however. As I read your explanation, if both strains had the exact same doubling time of 6.5 days, one strain would still be ln(2) *6.5/6.5 = 0.69 more infectious than the other one, so I must be misunderstanding.
We are trying to solve for the selection coefficient, which I interpret as “how much of an advantage does this strain have over the previous strain”.
It is here that I realize I don’t know how the Wikipedia editor found the 6.4 number, I couldn’t find it anywhere in the citation. The calculation they perform with the log odds comes from the YouTube video, which in the cited segment is actually talking about a different lineage, B.1.177 (this is different from B.1.1.7 ! Did the editor confuse these two?)
Logistic growth model indicates VUI grows +71% (95%CI: 67%-75%) faster per generation (6.5 days)
Limitations: Sample frequency is noisy & overdispersed in ways not captured by this model
So it turns out that this log odds calculation is not relevant to how we get this “70%” number, it was actually simply interpolated from the data by performing a logistic regression.
EDIT: I have now edited Wikipedia to remove the original calculation using the log odds.
Thanks for the explanation. I do not understand the formula however. As I read your explanation, if both strains had the exact same doubling time of 6.5 days, one strain would still be ln(2) *6.5/6.5 = 0.69 more infectious than the other one, so I must be misunderstanding.
Good catch! I watched the section of the YouTube video linked by the citation on Wikipedia, and the original formula they give is this:
ddtlog(odds_ratio)=selection_coefficientgeneration_time
We are trying to solve for the selection coefficient, which I interpret as “how much of an advantage does this strain have over the previous strain”.
It is here that I realize I don’t know how the Wikipedia editor found the 6.4 number, I couldn’t find it anywhere in the citation. The calculation they perform with the log odds comes from the YouTube video, which in the cited segment is actually talking about a different lineage, B.1.177 (this is different from B.1.1.7 ! Did the editor confuse these two?)
Reading the slide deck more closely, it says:
So it turns out that this log odds calculation is not relevant to how we get this “70%” number, it was actually simply interpolated from the data by performing a logistic regression.
EDIT: I have now edited Wikipedia to remove the original calculation using the log odds.