Exercise 4 Page 342

We have been told that the scores on a test are normally distributed with a mean of 74 and a standard deviation of 8. We will find the percentage of juniors whose score is below 66. x≤ 66 First, let's find the difference between the mean and 66. 74- 66= 8 Then, we will divide the difference by the standard deviation 8. 8/8=1 Thus, 66 is 1 standard deviation below the mean. To find the percentage, we will shade the percentage of data which is no less than 1 standard deviation below the mean.

Finally, we can find the percentage of juniors whose score is below 66 by adding the percentages of the shaded areas.

The percentage of juniors whose score is below 66 is 16 %.