Question

The producer of HB pencils has 720 pencils randomly chosen from each day's productions. A defect rate of 15% is acceptable.
a) Assuming that 15% of all manufactured pencils are defective, what is the probability of finding at least 80 percent defective pencials in this sample?
b) If 120 pencils are found to be defective in today's sample, is it likely that the manufacturing process may need improvements? Explain....

Answer 1

I probably read this problem wrong, but wouldn't (a) be a trick question? If you take 15% defected pencils out of however many regular pencils, that particular sample will be all defected, wouldn't it? Like I said, I probably read it wrong, so plz wait for a different answer. :-)

Answer 2

Besides, did you realize you posted the same question within less than an hour? Please be patient with these people-- they're doing their best.