when finding z score from a given probability, how do I know which value I should use?
for example i need to find value of .90 = do I use 1.26, 1.27, 1.28, or 1.29? they all can be rounded to .90. Please help!

Question

when finding z score from a given probability, how do I know which value I should use? 
for example i need to find value of .90 = do I use 1.26, 1.27, 1.28, or 1.29? they all can be rounded to .90. Please help!

mhchen · Answer

To find the z-score given a probability, you need to use a calculator or use Table A.

There's no mathematical 'formula' to find the z-score from the probability really.
You use TI Nspire calculator?

mhchen · Answer

Also when you say 'value of .90', you mean from 0 to 0.9 right?
Assuming it's that way, I used my calculator and I got
1.28155 which is closest to 1.28

jdanmath · Answer

i dont have a calculator. I was told to use a chart