Facebook recently examined all active Facebook users and determined that the average user has 183 Facebook friends. Suppose that the population of number of Facebook friends of a randomly selected user has a standard deviation of \sigmaσ = 241. Facebook draws a SRS of 250 Facebook users. What is the probability that the average number of Facebook friends is less than 175? Apply the Central Limit Theorem.
Given,
= 183 ,
=
241
Using central limit theorem,
P(
< x) =
P(Z < x -
/
)
So,
P(
< 175) =
P(Z < 175 - 183 / (241 / sqrt(250) ) )
= P(Z < -0.5249)
= 1 - P(Z < 0.5249)
= 1 - 0.7002
= 0.2998
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