From a shipment of 300 light-bulbs, a sample of 60 was selected at random and tested. If 18 light-bulbs in the sample were found to be defective, how many defective light-bulbs would be expected in the entire shipment?

Question

anonymous · Answer

90 I think

anonymous · Answer

18/60=.3 or 30%
So P(Defective item from shipment)=.30    (Equation 1)
     This is the probability             equals   30 percent

But P(Defective item from shipment)=n/300 (Equation 2)
where n is the number of defective light bulbs over the entire population, here it is equal to 300
Now set Equation 2 (right hand side) equal to Equation 1 (right hand side)
n/300=.30  
n=.30*300=90  (multiplied left and right hand side of the above equation by 300
So that means you expect to have 90 defective light bulbs in the entire shipment

anonymous · Answer

Really there are many different ways to explain this but it depends what class it is for (there are many probability classes out there)...

goformit100 · Answer

90 IS CORRECT