Question

Pinterest claims that 0.3005 of their app users are men. In a sample of 94 randomly chosen app users, what is the probability that between 28 and 31 (inclusively) of them will be men?

Answer 1

Probability = p = 0.3005

Sample size = n = 94

We have to find the probability that between 28 and 31 (inclusively) of them will be men.

That is we have to find the P( 28 X 31)

P( 28 X 31) = P(X = 28) + P(X = 29) + P(X = 30) + P(X = 31)

P(X = 28) = 0.0895

( Using excel =BINOMDIST(28,0.3005,94,0))

P(X = 29) = 0.0875

( Using excel =BINOMDIST(29,0.3005,94,0))

P(X = 30) = 0.0815

( Using excel =BINOMDIST(30,0.3005,94,0))

P(X = 31) = 0.0723

( Using excel =BINOMDIST(31,0.3005,94,0))

P( 28 X 31) = P(X = 28) + P(X = 29) + P(X = 30) + P(X = 31) = 0.0895 + 0.0875 + 0.0815 + 0.0723 = 0.3308