A survey finds customers are charged incorrectly for 2 out of every 10 items. Suppose a customer purchases 13 items. Find the probability that the customer is charged incorrectly on at most 2 items.The probability that the customer is charged incorrectly on at most 2 items is...

Answer 1

this is a binomial probability ... (c + i)^13 ... sum the 1st three terms

(13C0 * .8^13) + (13C1 * .8^12 * .2 + (13C2 * .8^11 * .2^2)

Answer 2

(0.2)^0 (0.8)^13+
(0.2)^1 (0.8)^12+
(0.2)^2 (0.8)^11
= 0.5017

Answer 3

what about the term coefficients?