# Z-Scores.. tell me if im right please!

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• Jan 27th 2006, 02:18 PM
Arbitur
Z-Scores.. not sure how to figure this one out
Will post what I got when I get something!.. heh dont let me not having an answer stop you ;/
For the second one i got aprox .39% of the population.
got 40 for the first one

I think I have those please help with the second image.
For the second one i think it is 12 and 0 respectively, not sure how to calculate the third one. got 69 for C

hah.. please help with the third one :(
• Jan 28th 2006, 12:18 AM
jacs
Solution for question 6

to figure out the z score use this formula:

$
z = \frac{score - average}{standard deviation}
$

mean = 50 sd = 10 and z = 1

$
1 = \frac{x - 50}{10}
$

10 = x - 50

x = 60
• Jan 28th 2006, 02:37 PM
ThePerfectHacker
What does it mean z-score and how does it work?
• Jan 28th 2006, 02:52 PM
CaptainBlack
Quote:

Originally Posted by ThePerfectHacker
What does it mean z-score and how does it work?

z score is the result of transforming a RV $X\sim N(\mu,\sigma^2)$ by letting:

$z=\frac{x-\mu}{\sigma}$.

Then $Z\sim N(0,1)$.

In rough terms it is the transform that is applied to allow the use of tables
of the standard normal distribution to be used to obtain probabilities for
random variables which have a normal distribution which is not standard.

RonL