# Simple Central Limit Theorem question.

• November 11th 2009, 05:49 PM
Oblivionwarrior
Simple Central Limit Theorem question.
Suppose that samples of size http://edugen.wiley.com/edugen/share...=1257993134069 are selected at random from a normal population with mean 100 and standard deviation 10. What is the probability that the sample mean falls in the interval from http://edugen.wiley.com/edugen/share...=1257968287857 to http://edugen.wiley.com/edugen/share...=1257968287857 ?

I'm not sure if I did this correctly, have I made any mistakes?

$\sigma$x = $\frac{\sigma}{\sqrt{n}}$ = 2

then for the lower interval I get 100-2.2(2) = 95.6
and for the upper interval 100+1.2(2) = 102.4

So P(95.6 < X < 102.4) --> P((95.6 - 100)/2 < Z < (102.4-100)/2) -->
P(-2.2 < Z < 1.2) --> P(1.2) - P(-2.2) and from the Z chart
0.884930 - 0.013903 = 0.871027
• November 12th 2009, 09:25 PM
matheagle
fill in the red ex's
This is not a central limit question since you do have normality