A teacher wishes to \"curve\" a test whose grades were normally distributed with

Question

A teacher wishes to "curve" a test whose grades were normally distributed with a mean of 66 and standard deviation of 14, The top 10% of the class will get an A, the next 30% of the class will get a B, the next 30% of the class will get a C, the next 20% of the class will get a D and the bottom 10% of the class will get an F. Find the cutoff for each of these grades. (Round your answers to two decimal places.) (a) The A cutoff is a grade of (b) The B cutoff is a grade of (c) The C cutoff is a grade of (d) The D cutoff is a grade of

Explanation / Answer

here for top 10 % ; z score =1.2816

a)therefore A cutoff is a grade of =mean +z*std deviation =83.94 ( for z with two decimal places answer is 83.92)

for 60 percentile ; z score = 0.2533

b)B cutoff is a grade of =mean +z*std deviation =69.55 (for rounding of z; cutoff =69.50)

for 30 th percentile ; zscore =-0.5244

c)C cutoff is a grade of =mean +z*std deviation =58.66 (for rounding ; cutoff =58.72)

for 10th percentile ; zscore = -1.2816

D cutoff is a grade of =mean +z*std deviation =48.06 (for rounding cutoff =48.08)

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