Grading Curve Option I Originally, Dr. Smith decides to curve his students’ exam
ID: 3371176 • Letter: G
Question
Grading Curve Option I
Originally, Dr. Smith decides to curve his students’ exam grades as follows:
Students whose scores are at or above the 90th percentile will receive an A.
Students whose scores are in the 80th – 89th percentiles will receive a B.
Students whose scores are in the 70th – 79th percentiles will receive a C.
Students whose scores are in the 60th – 69th percentiles will receive a D.
Students whose scores are below the 60th percentile will receive an F.
3. Find the z-scores that correspond to the following percentiles.
90th percentile – The area under the normal standard curve is 90%, or 0.90, to the left of z.
Therefore, z = 1.2816. 90th percentile = ? + z * ? = 78 + 1.2816 * 8 = 88.2528
80th percentile – The area under the normal standard curve is 80%, or 0.80, to the left of z.
Therefore, z = 0.8416. 80th percentile = ? + z * ? = 78 + 0.8416 * 8 = 84.7328
70th percentile – The area under the normal standard curve is 70%, or 0.70, to the left of z.
Therefore, z = 0.5244. 70th percentile = ? + z * ? = 78 + 0.5244 * 8 = 82.1952
60th percentile – The area under the normal standard curve is 60%, or 0.60, to the left of z.
Therefore, z = 0.2533. 60th percentile = ? + z * ? = 78 + 0.2533 * 8 = 80.0264
4.Using that information, find the exam scores that correspond to the curved grading scale.
Assume that the exam scores range from 0 to 100. (Round to the nearest whole number.)
A:_____- 100
B:
C:
D:
F:_____- 0
I have completed the question, but I am uncertain as to how the grading should be.
Would an A be 88 - 100
B 85 - 87 (or should it be 85 - 88??) I have confused myself. I am thinking it should be 85-87 because if an 88 is listed on B and A, what grade would the student get?
C 82 - 86
Thank you for any help!
Explanation / Answer
As per Caclualtion, For grading A or 90 percentile score should be 88.2582 - 100.
Now, if we round of we can say that it should be 88 to 100.
But in actual its 88.2582. So, any thing above 88 will fall in grade A
And anything from 85 to 88 will fall in B i.e If its 88 it will fall under B only.
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