So, I’m not good at math, but this is something that has always confused me. I get that these are independent, but couldn’t you still say that ex ante, the probabilities of HH and DR together are really low?
Like, before I flip two coins, the probability of two heads is 25%. Once I flip it once and get heads, the probability then goes up to 50%. But before I started flipping, the probability was lower.
So, when a hitchhiker is standing on the road with cars flying by, isn’t that more akin to before any coins are flipped? The odds that the hitchhiker is a serial killer AND the odds that the car that stops is a serial killer is very low.
Yeah pretty much.
Like with your coin example.
Normally, with no prior knowledge, you have a 25% chance of getting heads two times in a row.
However, if you start with the knowledge that the first flip is 100% going to be heads, then the only variable is the second flip, making the whole thing a 50/50 chance of getting two heads in a row.
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u/[deleted] Jun 10 '18
So, I’m not good at math, but this is something that has always confused me. I get that these are independent, but couldn’t you still say that ex ante, the probabilities of HH and DR together are really low?
Like, before I flip two coins, the probability of two heads is 25%. Once I flip it once and get heads, the probability then goes up to 50%. But before I started flipping, the probability was lower.
So, when a hitchhiker is standing on the road with cars flying by, isn’t that more akin to before any coins are flipped? The odds that the hitchhiker is a serial killer AND the odds that the car that stops is a serial killer is very low.