Question

statistics

The lengths of 3-inch nails manufactured on a machine are normally distributed with a mean of 3.0
inches and a standard deviation of .009 inch. The nails that are either shorter than 2.98 inches or longer than 3.02 inches are unusable. What percentage of all the nails produced by this machine are unusable?
not sure how to determine this

Answer 1

wait is it just P(x<2.98) + P(x>3.02)??

Answer 2

I was going through all this trouble solving it, then I read your answer =]
Yes P(3.02<x<2.98) = P(x<2.98)-P(x<3.02) would do

Answer 3

ah thought so thanks!
also would it not be
P(x<3.02) - P(x<2.98)? (if it were the other way around the probability would be negative right?)

Answer 4

Sorry you're right !

Answer 5

Then it's just calculating the z score and looking it up in the table =]

Answer 6

yup thanks again!!

Answer 7

Anytime !