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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
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Quote:
 Originally Posted by rihnavy 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.
The Z-value 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
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Quote:
 Originally Posted by rihnavy 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
You're missing grouping symbols.

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.

### required probalitity

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