The distribution of scores on a test is mound-shaped and symmetric with a mean score of 78. If 68% of the scores fall between 72 and 84, which of the following is most likely to be the standard deviation of the distribution?
A) 6
B) 2
C) 3
D) 12 3 Use Chebyshev's Rule

Question

Quizplus · Accepted Answer

In a normal distribution, approximately 68% of the data falls within one standard deviation of the mean. Since 68% of the scores fall between 72 and 84, the range from 72 to 84 represents one standard deviation on either side of the mean (78). The difference between 78 and 72 (or 84) is 6, indicating a standard deviation of 6.

The Distribution of Scores on a Test Is Mound-Shaped and Symmetric