Chapter 11.1, Problem 18E

To determine

To find: the probability where $x-value$ is in the given interval.

Answer to Problem 18E

The probability where $x-value$ is in the given interval is $P\left(x\le 21\right)=0.0015$

Explanation of Solution

Given:

Mean is 33

Standard deviation is 4

At most $21$ .

Calculation:

The value $21$ represents $\mu -3\sigma$ that is three standard deviations below mean.

Now, comparing the first and second diagrams, the probability that a randomly selected $x-value$ lies below $21$ is given by

  $P\left(x\le 21\right)=0.0015$

Conclusion:

Hence, the probability where $x-value$ is in the given interval is $P\left(x\le 21\right)=0.0015$