Exam scores for standard deviation of 12. The professor will assign letter a cer

Question

Exam scores for standard deviation of 12. The professor will assign letter a certain exam were approximately normally distributed with a mean of 72 and grades in the following way: Lowest 10% receive an F Highest 5% receive an A Middle 50% receive a C Those between an A and C receive a B and those between a C and F will receive a D. Answer each of the following (round to two decimal places) Those with scores above- will get an A Those with scores above and below will receive a B Those with scores above_a Those with scores above and belowwill receive a C and below will receive an F. will receive a D Those with scores below

Explanation / Answer

as we know that corresponding score =mean +z*std deviation

for top 5% ; at 95th percentile z =1.645

hence those with score above =mean +z*std deviation =91.74 will get an A.

for 75th percentile ; z =0.6745

hence those with score above 80.09 and below 91.74 will get an B

for 25th percentile z =-0.6745

hence those with score above 63.91 and below 80.09 will get an C

for bottom 1o percentile; z =-1.2816

hence those with score above 56.62 and below 63.91 will get an D

those with score below 56.62 will receive and F.

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