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Comment by jazoom | Hacker News Reader

n=1 (To reduce the number of email notifications I'm getting I'd best put this message in parentheses right next to this statement. NOTE: I'm not a statistician and don't believe statistics are all that important here! All I meant to say here is that this is a single incident. That's it. Nothing more.)

Edit: I'm getting the impression some people think I am suggesting there aren't grounds to suspend Uber's driving based on my 3 character comment above, so I'll paste my comment to a child comment here. Also, I'm not a statistician and I don't really care about the statistics here all that much when there's video evidence showing this was poor driving.

"Same reason clinical trials stop early if someone dies. It might just be bad luck. Unfortunately we'll never know and that drug might never be tested again. It might have been an amazing drug. In this case, based on how it played out, I personally wouldn't want Uber's self-driving cars near me."

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Using the above numbers as an example... from this sample size, we can be fairly confident that the current Uber fatality rate is greater than the sober human fatality rate (assuming that the Uber rate is 1 fatality every 3m miles and the human rate is 1 every 100m miles). Here, T is in "millions of miles".

    > poisson.test(1,3,1/100, alt='greater')
    
    	Exact Poisson test
    
    data:  1 time base: 3
    number of events = 1, time base = 3, p-value = 0.02955
    alternative hypothesis: true event rate is greater than 0.01
    95 percent confidence interval:
     0.01709776        Inf
    sample estimates:
    event rate 
     0.3333333

So if there isn't enough data to use statistics, they need to go with what they've got. And what they've got is a video that shows that it failed in a way that is inexcusable. It can't be explained as "this was a fluke accident, the car just happened to look away at the exact wrong time". Self-driving cars don't look away.

Mentioning the statistics might only makes sense if someone is to claim that, statistically, Uber's self driving fleet is safer. Well, it's not.

Any way you look at it, we don't have a reliable indicator to say they are safe enough. Maybe at some point we'll get more information, and realize that, indeed, this was a highly unlikely combination of things that is unlikely to happen again. But we don't have this now, so AZ was right to do this.

n =/= 1

If a baseball player has 10 at bats, and gets 0 hits, he's 0/10, with n=10

If same baseball player has 500 at bats, and gets 0 hits, he's 0/500, with n=500

You can be a lot more confident that he won't get his 1st hit anytime soon from the 2nd case compared with the 1st case. Because the sample size is significantly larger, even though the # of successes is equal between the two cases.

Agreed, but it's not like it's OK to say "Well sure, so far we have a kill rate of 50x a human driver, but why don't we wait until Uber kills at least 20 people first so we can determine proper statistical significance"

Why not?

Why in this case is it acceptable to make decisions on non-statistically significant data? You would exercise more rigour than that in a throwaway A/B test.

Same reason clinical trials stop early if someone dies. It might just be bad luck. Unfortunately we'll never know and that drug might never be tested again. It might have been an amazing drug.

In this case, based on how it played out, I personally wouldn't want Uber's self-driving cars near me.

It is statistically significant, at a 0.03 level: https://news.ycombinator.com/item?id=16655081

Excellent

Yes, but given that the probability of an auto death is continuous, there is an incredibly high confidence level that Uber is, in fact, less safe then human drivers.

No, bad statistician, don't pass go. N = 3,000,000. Miles are the observation here. We're talking # of mortalities per mile, so mile is the N. If you want to talk about the problem of only have a single mortality incident, you need to do the work of determining the likelihood of a 1 in 100,000,000 observation incident occurring in the first 3,000,000 observations. I leave that detail to the students.

Then that number becomes arbitrary. If it was measured in deaths per lightyear your 'n' would become 0.

You know what I meant when I said "n=1".

No, i dont know what you mean. I know only that your comments do not portray a deep understanding of statistics and probability. Do your own homework to determine the liklihood of a low probability event ocurring within a small number of observations. That is you answer to the question of how meaningful it is that Uber experienced a fatality in only 3,000,000 miles.

You're being pompous. I never claimed to have those things.

Re-read my original comment with my edit and you will see why I believe your statistics in fact do not answer the question of how meaningful Uber's fatality is. I doubt your expert testimony of pedantic statistics will trump common sense and the video evidence.

It’s ironic, but true that telling someone they’re pompous is almost always in itself, very pompous. In general I find that making a reasoned argument is inevitably more valuable and convincing than calling people names.

Calling names is saying: "you are a pompous person". It is very different to saying "you are being pompous".

And you accused someone else of pedantry!

@bitumen, calling names is saying: "you are a pompous person". It is very different to saying "you are being pompous".

I have pointed out an error in your statistical reasoning. This is not a matter of pomposity or opinion. No insult was intended, and i retract the snark. My criticism of your statisitcal reasoning, however, stands.

I have no problem with people pointing out errors and new ideas to me. It's how we learn. That's not what I was referring to.

It was more the calling me a "bad statistician", the "do not pass go", the "leave the details to the students", commenting on my understanding of statistics and probability, telling me to "do my homework" and telling me how to get the answer to a question I didn't pose.

I'm not upset and I don't hold it against you. I know the written word can sometimes be more difficult to interpret. I appreciate your retraction.

You crossed into incivility in this subthread and provoked a pointless spatty flamewar. Please don't do that again. There's no reason not to be respectful, regardless of how much you know about statistics.

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