Binomial Distributions Question
Im having trouble doing this question.
Could someone help me out.
A factory produces computer chips with a 0.9% defect rate. In a batch of 100 computer chips, what is the probability that
a) only 1 is defective?
b) at least 3 are defective?
I guessed that p = 0.9 and q = 0.1 and n = 100
For a) I tried (100 Choose 1)*(0.9)^1 * (0.1)^99
but it turned out wrong..
The answers in the back of the book were a) 36.8% and b) 6.2%
How did they get these values?
Thanks in advance