Question

WILL MEDAL AND FAN for best help.

A class's exam scores are normally distributed. If the average score is 65 and the standard deviation is 6, what percentage of students scored below 71? Hint: Use the 68-95-99.7 rule.


34%



50%



68%



84%

Answer 1

The score of 71 is one standard deviation above the average of 65. You can use the diagram to find the solution.

Answer 2

99.7?

Answer 3

@kropot72

Answer 4

Not really. From the diagram, what percentage of the data lies between -1 and 1 standard deviation from the mean?

Answer 5

68%

Answer 6

so the center of the graph is the standard deviation of the mean, not the mean its self.

Answer 7

The point marked zero is the normalized position of the mean. What percentage of the data lies between -1 and -3 standard deviations from the mean.

Answer 8

oh i already answered that one...... did i misunderstand it?

Answer 9

50% of the data lies to the left of the mean.
68/2=34% of the data lies between the mean and -1 standard deviation from the mean.
Therefore the percentage of the data lying between -1 and -3 standard deviations from the mean is approximately given by 50 - 34 = 16%.