Comment by stetrain
2 days ago
> If I toss a coin four times and it comes up heads three and tails once, it doesn’t mean that there’s a 75% chance that this coin lands heads up.
No, but it means that to ensure that I do better on my next set of coin tosses I need to beat 3 in 4, not 1 in 2.
But you doing better is independent of the risk involved. The chances of you getting 3/4 heads or better is around 31%, so theres ~69% chance you’ll do worse next time round. Doesn’t change the fact that each coin toss is still 50/50.
> Doesn’t change the fact that each coin toss is still 50/50.
That assumes a fair coin. The fact is you don't know what the odds were of getting heads or tails for that particular coin, all you know is that you got 3/4 heads. And in this analogy, a few hundred coins have every been made, in maybe a dozen styles, none of which have been fair, so you have no good reason to believe that this particular coin should have 50/50 odds of landing heads up.
But the idea we're exploring is that the coin is fair (i.e. the 1/1000 estimate is correct, and the Apollo missions were unlucky).
The original discussion was about acceptable mortality rate. Artemis's target is 1 in 30, which is better than the empirically observed mortality rate of the actual Apollo missions. The mortality rate is a target. And if that target is an improvement over the actual outcome of the Apollo missions, I think it's difficult to say that the target is weaker than Apollo's, which was the claim up the thread that I was responding to.
The public doesn't care if Apollo had a theoretical risk rate lower or higher than 1/12, what they saw was that 1/12 missions resulted in the death of the crew. The NASA administrator explaining that their estimated risk was only 1/1000 doesn't change the real-world perception or outcome.
I think we're approaching this from different angles. 1 in 30 is better than the observed rate, but worse than the estimated rate.
FWIW, the 1/12 is also actually off, the long-term mortality rate for Apollo astronauts is high.
But so is the 1/1000, Nasa's own estimates were so bad that they decided it was bad optics to keep doing them - https://ntrs.nasa.gov/api/citations/20190002249/downloads/20...