Problema Solution
Facebook reports that the average number of Facebook friends worldwide is 175.5 with a standard deviation of 90.57. If you were to take a sample of 25 students, what is the probability that the mean number Facebook friends in the sample will be 190 friends or more?
Answer provided by our tutors
Formula to be used: P(X>190)=P((X-mean)/s
sqrt of the sample is = 5, so s becomes (90.57/5.)
(190-175.5)/(90.57/5) = 0.80
P(Z>0.8)=0.2119 (check standard normal table)
there is approximately a 21% probability that the mean number of Facebook friends in the same will be 190 friends or more