An urn contains 2 red and 2 green marbles. We pick a marble, record its color, and replace it. We repeat this procedure a second and a third time. The probability distribution for the number of red marbles is given below.

For this distribution, the probability of exactly one red marble is given by:
A)1/8.
B)3/8.
C)7/8.
D)1/3.

Question

An urn contains 2 red and 2 green marbles. We pick a marble, record its color, and replace it. We repeat this procedure a second and a third time. The probability distribution for the number of red marbles is given below.

For this distribution, the probability of exactly one red marble is given by:

For this distribution, the probability of exactly one red marble is given by:
A)1/8. 
B)3/8. 
C)7/8. 
D)1/3.

Quizplus · Accepted Answer

The probability of exactly one red marble is given by adding up the probabilities of RGG, GRG, and GGR (order doesn't matter). Each of these has probability 1/2 * 1/2 * 1/2 = 1/8. So, the total probability is 3/8. Therefore, the answer is B.

An Urn Contains 2 Red and 2 Green Marbles