Question

Conditional probability question. Help!
The weather conditions for Wednesday are as follows: There is a 90% chance of snow; there is a 30% chance of rain and hail; there is a 40% chance of rain. What is the conditional probability that it will snow given that it is already raining?

Answer 1

is this a trick?

i would say zero, since if it is raining it is not snowing

Answer 2

I don't think it was a trick because it was on a test I took for my tutoring work and there were answers (which I don't remember) and none of them was 0%. There was a formula for conditional probability which was something like P(A/B)/P(B) or something like that, but the formula did me no good. Can you help or no?

Answer 3

Maybe you mean rain and snow instead of rain and hail?

Answer 4

it is the probability of snow and rain divided by the probability of rain

Answer 5

but you are not given the probability of snow and rain
and i would assume (really) that it is zero

Answer 6

Actually I reread it several times thinking that it should have said rain and snow and not rain and hail, but it did say rain and hail, which to me is a piece of useless info. I thought maybe they were trying to trick us, giving us info we didn't need, seeing if we could pick out and use what we DID need. Idk.

Answer 7

i have never seen it rain and snow at the same time

Answer 8

"it is the probability of snow and rain divided by the probability of rain". What do you do with these probabilities? Do you add them or multiply them?

Answer 9

I guess you treat the snow/rain events as independent, so the numerator is the product of the probabilities of snow and rain

Answer 10

I don't know if they were saying it would rain AT THE SAME TIME as it would snow, only that it would snow sometime during the day.

Answer 11

@SithsAndGiggles that seems really unlikely

Answer 12

satellite

Answer 13

@satellite73 it does, but the question doesn't say we're not on some planet with crazy and sudden climate/temperature change.

Answer 14

and in any case if you are assuming they are independent, then the probability it snows is 90% irrespective of whether it is raining or not!

Answer 15

We can all agree the question is poorly phrased :P

Answer 16

I don't remember the solutions they gave...only that one of them was 10%. I wish I could remember! I will try and find out verbatim what the problem says and all its solutions and then repost. How does that sound? You guys are great...thanks for the help!

Answer 17

love to see it!

Answer 18

satellite