The standard deviation of 60% of 250?

Question

Hi Guys, may I please get help with this one problem:

60% of the computer chips produced at a factory are good; the others are defective. A box contains 250 chips from the factor. Let X be the number of good chips in the box. what is the standard deviation of the number of good chips in the box?

is the answer square root of (250*0.6)?
Thank you!

Answer 1

If the question is actually saying that you have taken a sample of size 250 from the (much larger) population then s.d is sqrt(250*.6*.4)  i.e. sqrt (npq).