Posted by **pat** on Tuesday, December 11, 2012 at 9:45pm.

6. 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?

- statistics -
**PsyDAG**, Thursday, December 13, 2012 at 1:36am
Z = (score-mean)/SEm

SEm = SD/√n

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to your Z score.

- statistics -
**Joseph**, Saturday, May 4, 2013 at 2:42am
Solution

My mean is 175.5

My standard deviation is=90.57

Sample=25

So the probability is

Formula to be used: P(X>190)=P((X-mean)/s

sqrt of my sample is = 5

(190-175.5) / 90.57/5)

14.5 / 18.114

calculator says 0.8004858120790548746825659710721

I check the z-table and I see -.8 under the z of 0.00 correlates to .2119

=0.2119

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