A statistics instructor has decided to grade on a curve that results in the foll

Question

A statistics instructor has decided to grade on a curve that results in the following distribution: A's - top 10% of students'& - next 20% of students; C's - middle 40% of students; D's - next 20% of students; F's - bottom 10% of students. If the exam has a mean grade of 75 with a standard deviation of 15, what exam scores would border each titter grade (provide answers to the nearest integer)? A's would be students with scores above B's would be grades above and up to_ C's would be grades above and up to_ D's would be grades above and up to_ F's would be grades at or below_ What exam scores would border each letter grade if the exam had a mean of 80 with a standard deviation of 5 (provide answers to the nearest integer)? A's would be students with scores _ B's would be grades above and up to_ C's would be grades above and up to_ D's would be grades above and up to_ F's would be grades at or below_ Is grading on a curve always a benefit to every student? Who do you think it benefits and when? How would you feel with a grade of 72, 82, and 92 in each case? (This input box will not be automatically graded, but will be reviewed by the instructor.)

Explanation / Answer

Will do the 1st question:

From the Z tables we find Z values and then denormalize the Z values into scores using params of normal distributions:

A - should have a Z score of 1.28
Score for boundry A = 75+15*1.28 = 94.2
B - should have a Z score between .525 and 1.28
Score for 82.875 to 94.2
C - should have a Z score between -.525 and .525
Score for 67.125 to 82.875
D - should have a Z score of -.525 to -1.28
Score for 55.8 to 67.125
E - shoudl have a Z score of -1.28
Score for boundry E = 75-15*1.28 = 55.8

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