Tesla’s Driver Fatality Rate is more than Triple that of Luxury Cars
medium.com
medium.com
This sounds like a good basis of a line-by-line refutation or counterargument on Medium. :)
What he did there is statistically unacceptable.
The medical equivalent would be to compare side effect profile of current best of line treatment done in general populace to results to your new treatment's phase 1 trial results which is done in healthy people only. Then advertise that.
Regardless, can we have the raw data please? Are the rates even meaningful when the incident counts are low? Vehicle years are not the right unit as this counts cars that are not being driven. Actual range driven is the right unit.
That one local death in NL, the guy did double the allowed speed on a stretch where I can hardly hit 20% above the allowed speed accounting for traffic lights and local situation. The one Tesla death with the young kid, the same. Don't put maximum traction hundreds of HP in male hands. We tend to use it (sometimes).
Moreover, they should use the data where miles drive is available, say, from taxi drivers. Oops, that's 0 out of 0 total? :)
For such low incidences, even studentising will not produce right confidence intervals based on normal distribution. Poisson distribution cannot even be used, direct binomial instead, because it is likely that the error due to approximation will be important. (calculate from rule of rare events)
The least they could do is run the same stats for both Tesla and another luxury brand (say, Audi), and then compare like to like.
Does anyone have experience doing survival analysis? I've read a lot of the documentation of CamDavidsonPilon's Lifetimes. maybe i'll give it a shot, seems like the type of thing people would already do to price car insurance
Tesla’s mortality rate (41 deaths per million vehicle years) is so much higher than the average luxury car (13 deaths per million vehicle years) that when comparing the two, the difference is hugely statistically significant. The difference is 28 additional deaths per million vehicle years, with a confidence interval of 11 to 63, and a p-value of 0.0001.
Binomial confidence intervals for individual cars except Tesla provided by IIHS
Binomial confidence intervals for Tesla and groups using Conflint.xls from John Pezzullo
so he is doing some kind of hypothesis testing, using the binomial distribution but I wish he would post the data and spreadsheets used to generate everything. probably some p-hacking going on?
I'm not really that statistically literate, just a computer engineering dropout if someone could explain that'd be cool
The author then went on google and tried to find more articles. Included whatever he could find only for Tesla.
If you're going to go through extra steps to pump Tesla's numbers, then of course they're going to be higher.
Duh.
It's so long because the author needs to jump through too many hoops to end up where he wants to go. Audi A6 has 0 causalities? Cool. Tesla has 0 in one year? Extremely suspicious. Not enough Tesla accidents in the database? Include China. Should he include China for the other cars? Nah.
This article is a joke.
I don't think this article was written in good faith.
Now maybe all the brands have the same problem with missing data, but that would mean fatalities across the board are much higher than reported by the insurance agency funded research firm. That doesn’t seem as likely to me, but I do believe more research needs to be done.
The US had 12.9 fatalities per 100k cars. China? 104.5 -- 8 times higher.
Come on. This is a joke.
> To have the largest sample size and best confidence intervals possible, we also included international accidents (three total, from Canada, Holland, and China). Given the higher incidence of fatal accidents per vehicle-year in China compared to the United States, and the lower incidence of fatal accidents in Holland and Canada, these three deaths should adjust to 3.63 deaths. However, for the sake of conservatism and to avoid a large debate about a rather small difference, we use 3.00 deaths in our analysis.
They looked for Tesla fatalities because they needed more to make the argument they wanted. You understand the distinction, right?
As disclosure, I'm long TSLA, both index and individual shares.
Yes, the authors are short Tesla, but they disclose it. Yes, the analysis is naive, but that doesn't necessarily mean its conclusions are off. Yes, the inclusion of data from China is... questionable, but the authors address it upfront: "To have the largest sample size and best confidence intervals possible, we also included international accidents (three total, from Canada, Holland, and China). Given the higher incidence of fatal accidents per vehicle-year in China compared to the United States, and the lower incidence of fatal accidents in Holland and Canada, these three deaths should adjust to 3.63 deaths. However, for the sake of conservatism and to avoid a large debate about a rather small difference, we use 3.00 deaths in our analysis."
Like most investors, I'm long TSLA. Both index and individual shares.
I would have liked to see the HN community rationally debate what to me looks like an earnest but naive analysis of fatality rates -- based on its merits or lack thereof. Instead, at least some in the HN community have resorted to ad hominem attacks ("Tesla short!") and flagging.
For the record, I'm a huge fan of Musk and the company, but other than minimal long exposure through passive funds, I have no position in Tesla.
Edit: Together with the highly dubious "statistical" analysis they did, this COULD suggest that the article is intended to create doubts about Tesla and thus drive the stock price down. However, this is of course speculation.