Student Needing Help

#1
I am lost with this question. Could someone please help?

A normal population has a mean of 20.0 and a standard deviation of 4.0.

Compute the z-value associated with 25.
 

JohnM

TS Contributor
#2
The z value or z score represents how many standard deviations a particular score is from its average or mean:

z = (x - mu)/s

x = the value at which we need a z score
mu = the average or mean
s = standard deviation

plugging in from your question:
z = (25 - 20) / 4 = 5/4 = 1.25

z = 1.25
 
#4
A normal population has a mean of 20.0 and a standard deviation of 4.0.

Compute the z-value associated with 18.

Am I able to apply the same problem with 18. Can I just replace the 25 with 18. I am still trying to figure this stuff out.