Question

A. According to an estimate, 50% of the people in the United States have atleast one credit card. If a random sample of 30 persons is selected, what is the probability that 19 of them has atleast one credit card?

PLIZ REALLY NEED HELP!!

THANKS VERY MUCH..

Answer 1

prob(having credit card ) = 1/2
prob(not having credit card ) = 1/2

I assume you want the prob that exactly 19 of the 30 people surveyed have a credit card.
If it is something like "at least 19" of the 30, it would become a rather tedious and long question.

prob(that 19 of 30 have a credit card
= C(30,19) (1/2)^19 (1/2)^11= C(30,19) (1/2)^30
= appr .05088