SOLUTION: A box of 30 flashbulbs contains 10 defective bulbs. A random sample of 2 is selected and tested. Let X be the random variable associated with the number of defective bulbs in the

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Question 1150083: A box of 30 flashbulbs contains 10 defective bulbs. A random sample of 2 is selected and tested. Let X be the random variable associated with the number of defective bulbs in the sample.
​(A) Find the probability distribution of X.
​(B) Find the expected number of defective bulbs in the sample.

Answer by VFBundy(438) About Me  (Show Source):
You can put this solution on YOUR website!
Part (A):

Probability of 2 defective bulbs in the sample: %2810%2F30%29+%2A+%289%2F29%29 = 9/87...(can be reduced to 3/29)
Probability of 1 defective bulb in the sample: %2810%2F30%29+%2A+%2820%2F29%29+%2A+%282%21%2F%281%21%2A1%21%29%29 = 40/87
Probability of 0 defective bulbs in the sample: %2820%2F30%29+%2A+%2819%2F29%29 = 38/87

Part (B):

2 * 9/87 = 18/87
1 * 40/87 = 40/87
0 * 38/87 = 0

18/87 + 40/87 + 0 = 58/87 = 2/3

The number of expected defective bulbs in the sample is 2/3...or, 0.6667.