More Calculations Involving The Normal Distribution - Finding Probabilities

Suppose we have a distributionWe will find

using the diagram on the left.

This corresponds to a probability of 0.6915 hence

Now we will find illustrated by the diagram on the left.

Ignoring the minus sign we go to the

normal distribution tables and look for the probability corresponding

to finding 0.7422. Because we had a negative value of

we subtract this from 1. We have found

Because the probabilities in the tables are all of the form

We subtract this value from 1 again to obtain

Now we use