Question

In a survey of 1000 social-media account holders aged 18 years and older conducted by a certain organization, it was found that 78% of them have one or two such accounts. If 10 of the participants in the survey are picked at random, what is the probability that at most 7 of them have one or two social-media accounts? (Round your answer to four decimal places.)

Answer 1

I'm going to reword your question so it's easier to answer. I'm also going to pretend no one has 3 or more accounts because it's irrelevant.

22% have no accounts (220/1000)

What is the probability that 4 or more of the 10 participants has no account?

(220/1000)*(219/999)*(218/998)*(217/997)*(10 choose 4)