Under the normal curve, between z scores of + 10, there are always
A) 100% of the cases
B) 95% of the cases
C) 68% of the cases
D) more than 99% but less than 100% of the cases

Question

Quizplus · Accepted Answer

The area under the normal curve between any two z scores is always between 0% and 100%. Since the z score of +10 is more than 3 standard deviations away from the mean, we know that more than 99% of the cases fall below this z score. However, since the normal curve extends indefinitely in both directions, we cannot say that we have captured 100% of the cases. Therefore, the best choice is D, which acknowledges that the area is greater than 99% but less than 100%.

Under the Normal Curve, Between Z Scores of + 10