# Normal Probability Distributions

Suppose the lifetime income of all high school grads is normally distributed and that the lifetime income of all college grads is normally distributed. Suppose that the difference in the means is known to be $600,000 and that the standard deviation of the high school graduates is $300,000 and the standard deviation of the college grads is $200,000. What percent of college grads earn more in a lifetime than the highest 40% of high school grads?

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#### Solution Preview

Assume the average income of high school grads is H, and the average income of college grads is C.

Then we know H-C =600,000

First, the highest 40% of a normal distribution has a ...

#### Solution Summary

Suppose the lifetime income of all high school grads is normally distributed and that the lifetime income of all college grads is normally distributed. Suppose that the difference in the means is known to be $600,000 and that the standard deviation of the high school graduates is $300,000 and the standard deviation of the college grads is $200,000. What percent of college grads earn more in a lifetime than the highest 40% of high school grads?