# Statistics

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A statistics professor gives a test and finds that the scores are normally distributed with a mean of 25 (out of 100) and a standard deviation of 5. She plans to curve the scores in one of two ways.

2) She could use the following scheme:
A: Top 10% earn A's
B: Scores above the bottom 70% and below the top 10% earn B's
C: Scores above the bottom 30% and below the top 30% earn C's
D: Scores above the bottom 10% and below the top 70% earn D's
F: Bottom 10% earn F's

If the professor uses the first method, what would the new mean and standard deviation be? Is this a fair method for curving?

If the professor uses the second method, what are the numerical limits for each letter grade?

Which method do you think is fairer? Why?

• Statistics -

Just remember, under 1) the distribution is still "tight" around the mean.

On 2) 10 precent get A's, and 10 percent get F's. Did they deserve them?

Fairer? Strickly opinion.

• Statistics -

Adding 50 points to each score only changes the mean. These tests are only ordinal scales.

http://www.members.cox.net/dagershaw/lol/TwoPlusTwo.html

The cutting points for grades are arbitrary and can vary from teacher to teacher and subject to subject.

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