Z-Score?

#1
Hi,
I'm having a problem figurung out what this question is asking:

"Find the number Z such that the proportion of observations that are less than Z in a standard normal distribution is 0.8."


I think it has something to do w/ standardizing and z-score I just don't know how...
 

JohnM

TS Contributor
#2
It's asking you to find the z score from the normal distribution table (in the back of your text) that divides the lower 80% of the area under the curve from the upper 20%.

Some tables give you areas from negative infinity to z, others from 0 to z.

For 0.8, z = 0.842.