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.

- probability that exactly half of our sample use Facebook?
- probability that at least 10 of our sample use Facebook?
- 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:

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