Question in a textbook: find the Z-score for 80% of the area centered on 0. I know how to look it up in a table - the answer is +/- 1.28 Does anyone know how to get this out from R?
If you use the qnorm function, you can get the z-score such that the area to the left of z is whatever you enter for the argument p. If you're looking for the middle 80%, then the positive z-score is the number such that 90% is to the left of it--80% in the middle plus 10% in the left tail.
> qnorm(0.9)
[1] 1.281552