Question

n a normal distribution, 31% of the items are under 45 and 8% are over 64.Find the

mean and standard deviation of the distribution​

Answer 1

Answer:

This is a classic example of finding mean and standard deviation using Z values.

From this page find the Z value corresponding to 31% area under the curve and 92% (100-8) percent area under the curve.

Note: You'll probably be given tables to lookup in your quizzes.. they're a bit confusing. But you might as well learn how to use it.

As you know:

Z=X−μσ

Put in X and Z values values twice, you'll have two linear equations. Solve them and the answer is yours!