In the back of your statistics text, there is a table labeled something like "areas under the normal distribution." Remembering that the Z score will be negative because it is below the mean, use it to find the Z value that has either .30 for the smaller side or .70 for the larger side.
I hope this helps. Thanks for asking.
for a standard normal curve, find the z-score that separates the bottom 30% from the top 70%
2 answers
.325