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October 19th, 2016, 01:48 PM  #1 
Newbie Joined: Oct 2016 From: United States Posts: 5 Thanks: 0  Probability & Central Limit Theorem The population mean and standard deviation are given below. Find the required probability and determine whether the given sample mean would be considered unusual. μx̄ = μ = 12,749 σ = 1.2 n = 35 For the given sample n = 35, the probability of a sample mean being less than 12,749 or greater than 12,752 is ____________ 
October 20th, 2016, 03:21 PM  #2 
Newbie Joined: Oct 2016 From: United States Posts: 5 Thanks: 0 
This is what I have so far. σx = σ/ √n = 1.2/ √35 = 0.2028 z = x̄  μx̄/σx = x̄  μx̄/σ/√n = 12,749  12,752/ 1.2√35 = 0.4226 = .33724 I stopped right there because I got confused. I'm stuck. 
October 21st, 2016, 12:10 AM  #3 
Senior Member Joined: Dec 2012 From: Hong Kong Posts: 853 Thanks: 311 Math Focus: Stochastic processes, statistical inference, data mining, computational linguistics  The Zvalue should be 14.79, not .4226  you might want to check that you did not erroneously punch the '*' button instead of '/'.

October 23rd, 2016, 06:57 AM  #4 
Newbie Joined: Oct 2016 From: United States Posts: 5 Thanks: 0 
Is the first equation that I have correct or should it be z= 12749  12749/1.2/√35 = 0

October 23rd, 2016, 01:28 PM  #5  
Banned Camp Joined: Jun 2014 From: Earth Posts: 945 Thanks: 191  Quote:
z = (x̄  μx̄)/(σ/√n) According to the problem, μx̄ = 12,749, not 12,752. If x̄ is supposed to equal 12,752, then z = (12,752  12,749)/(1.2/√35) ~ 14.79 That would be one part of the problem.  

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