Question

A company's records indicate that 90% are error free,if 8-records are randomly selected, what is the probability that at least 2 records have no errors.

Answer 1

this is a binary probability ... no error / error ... 90% / 10%

"at least two" means not one or zero

(n + e)^8 = n^8 + 8 n^7 e + ... + 8 n e^7 + e^8

subtract the last two terms from 1
... 1 - (8 * .9 * .1^7) - .1^8