In a large section of a statistics class, the points for the final exam are normally distributed, with a mean of7474and a standard deviation of99.Grades are assigned such that the top 10% receive A's, the next 20% received B's, the middle 40% receive C's, the next 20% receive D's, and the bottom 10% receive F's. Find the lowest score on the final exam that would qualify a student for an A, a B, a C, and a D.

Question

Asked Nov 23, 2019

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In a large section of a statistics class, the points for the final exam are normally distributed, with a mean of

7474

and a standard deviation of

99.

Grades are assigned such that the top 10% receive A's, the next 20% received B's, the middle 40% receive C's, the next 20% receive D's, and the bottom 10% receive F's. Find the lowest score on the final exam that would qualify a student for an A, a B, a C, and a D.

Expert Answer

Step 1

Given data

Mean = 74

Standard Deviation = 9

a)The Lowest Score for A grade is given by

p-value will be 0.90 for top 10%

Finding the value of z at p=0.90

z(p=0.90) = 1.28 ( From Excel =NORM.S.INV(0.90))

Step 2

b)The Lowest Score for B grade is given by

p-value will be 0.70 for top 30%

Finding the value of z at p=0.70

z(p=0.70) = 0.524 ( From Excel =NORM.S.INV(0.70))

Step 3

d) The lowest grade for Grade D is

p-value will be 0.10 for lowest 10%

Finding the value of z at ...

Image Transcription
X — и Z = X 74 9 о X 74 -1.28 9 X— — 1.28 х9+74 — 62. 48

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