4 ms·
The replies to this don't look correct so here's my take: P(R) = Probability of rain in Seattle P(F) = Probability of three friends saying it's raining i
by OptimalPlay 8y ago
The replies to this don't look correct so here's my take:
P(R) = Probability of rain in Seattle
P(F) = Probability of three friends saying it's raining in Seattle
P(F) = P(F|R)*P(R) + P(F|R')*(1-P(R))
= (8/27)*P(R) + (1/27)*(1-P(R))
= (7/27)*P(R) + (1/27)
P(R|F) = (P(F|R)*P(R))/P(F)
= [(8/27)*P(R)] / [(7/27)*P(R) + (1/27)]
= 8*P(R) / (7*P(R) + 1)
So, for instance, if the true probability of rain in Seattle is 50%, the probability of it raining in Seattle given our three friends are saying that it is raining in Seattle is 4/4.5 = 89%