[clairity]

> "We have a sample size of 1..."

i'm not sure that's the right way to look at it (that uber is a sample of 1, or that the death is a sample of 1).

in this case, the metric is deaths per mile, so there are purportedly 3 million samples for uber self-driving cars, with one positive (negative?) result in that sample. you need so many samples because the positive observation rate is expected to be very low (as evidenced by the 1.18 deaths per 100 million miles driven by human drivers).

if you assume the death rate is roughly the same, you can (roughly) estimate the expected error or confidence interval with the 3 million sample size versus a 100 million known rate for human drivers. as more samples are gathered, the confidence interval gets tighter: if the confidence interval currently stands at 80% with 3 million samples (made up numbers), it might go up to 85% with 6 million samples.