In: Statistics and Probability
A statistician is betting in a game of Counting Rates and
Probability. The game uses cards, but 1/3 of the cards are red, and
2/3 of the cards are black. If the statistician gets a red card his
face will blush 30% of the time. If the statistician gets a black
card his face will blush 60% of the time. Assuming you see the
statisticians face blushing, what is the probability he just drew a
black card?
Answer to 3 decimals
P(red cards) = 1/3
P(black cards) = 2/3
P(face will blush | red card) = 0.3
P(face will blush | black card) = 0.6
P(face will blush) = P(face will blush | red card) * P(red card) + P(face will blush | black card) * P(black card)
= 0.3 * 1/3 + 0.6 * 2/3
= 0.5
P(black card | face blushing) = P(face will blush | black card) * P(black card) / P(face will blush)
= (0.6 * 2/3) / 0.5
= 0.8 (ans)