A distribution of 400 scores is approximately normally distributed. The mean of the distribution is 50 and the standard deviation is 10. What percentage of scores are less than a value of 30?
A) about 2.5%
B) about 16%
C) about 34%
D) about 50%

Question

Quizplus · Accepted Answer

To find the percentage of scores less than a value of 30 in a normally distributed set with a mean of 50 and a standard deviation of 10, we calculate the Z-score for 30. The Z-score is (30 - 50) / 10 = -2. A Z-score of -2 corresponds to a percentile of about 2.5%, indicating that approximately 2.5% of the scores are less than 30.

A Distribution of 400 Scores Is Approximately Normally Distributed