Question

1. In May 2019, 69% of all adults in the U.S. said they use Facebook. We then took a random sample of 22 American adults.

1. probability that exactly half of our sample use Facebook?
2. probability that at least 10 of our sample use Facebook?
3. mean and standard deviation for the number of adults that use Facebook for the sample?

Answer 1

The number of American adults out of the 22 selected who use facebook could be modelled here as:

a) The probability that exactly half of the sample selected use FB is computed using the binomial probability function here as:

Therefore 0.0303 is the required probability here.

b) The probability that least 10 of our sample use Facebook is computed using the EXCEL function here as:

P(X >= 10)

=1 - P(X <= 9)

=1-binom.dist(9,22,0.69,TRUE)

The output here is 0.9941

Therefore 0.9941 is the required probability here.

c) The mean and standard deviation for the distribution here are computed as: