Math Help - Probability Question

1. Probability Question

A shipment of 10 items has two defective and eight nondefective items. In the inspection of the shipment, a sample of items will be selected and tested. If a defective item is found, the shipment of 10 items will be rejected.

If a sample of 3 items is selected, what is the probability that the shipment will be rejected?

I used f(x)=(nCr(2,x)*nCr(8,3-x))/nCr(10,3)
f(1)=.466667

Is the book right?

2. Originally Posted by lisakki
A shipment of 10 items has two defective and eight nondefective items. In the inspection of the shipment, a sample of items will be selected and tested. If a defective item is found, the shipment of 10 items will be rejected.

If a sample of 3 items is selected, what is the probability that the shipment will be rejected?

I used f(x)=(nCr(2,x)*nCr(8,3-x))/nCr(10,3)
f(1)=.466667

If X is the random variable number of defectives in sample, I'll bet that you only calculated Pr(X = 1) rather than $\Pr(X \geq 1)$, which is equal to 1 - Pr(X = 0) by the way.