Question

6. In a distribution 30% of the items are
under 50 and 10% are over 86. Find
the mean and standard deviation of the
distribution.​

Answer 1

I believe this is a homework question. So I won't give you the exact solution.

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!

Thank u