The test scores from a recent Mathematics test are as follows: 95.5,65.9,93.2,88.6,56.8,50,86.4,54.5,40.9,77.3,79.5,65.9,70.5,77.3,81.8,50,79.5,and 68.2.The mean score was 71.2 with a standard deviation of 15.5.If the Normal model is appropriate,what percent of the scores will be greater than 86.7?
A)15.87%
B)0.15%
C)10%
D)34%
E)2.28%

Question

Quizplus · Accepted Answer

To find the percent of scores greater than 86.7, we need to standardize this value:

z = (86.7 - 71.2)/15.5 = 1.00

Using a standard normal table or calculator, we can find the proportion of scores above z = 1.00 to be 0.1587 or 15.87%. Therefore, the answer is A.

The Test Scores from a Recent Mathematics Test Are as Follows