Question

Propose how to grade on a curve if you have a (i.) below-average class, an (ii.) average class, and an (iii.) above-average class. Which distribution(s) do you choose in each case? What are the values of its parameter(s)? Why do you choose those distributions? How will letter grades of A, B, C, D, and F be assigned?

Answer 1

Grade on a Standard normal distribution curve which can explain all of the three cases. If data is left of curve, then it is below-average class, if data on right, it is above-average class.

The parameter values of standard normal distribution are ~ N(0,1)

Note that this is practiced in most of institutes where a professor distribute student grades on normal distibution curve such that most of the students are at middle or average graded.

For letter grades A,B,C,D,E,F, divide normal curve area into 6 equal parts and for each z, assign a grade.

F - if z< -0.9674

E - if -0.9674 < z < -0.4307

D - if -0.4307 < z< 0

C - if 0 < z < 0.4307

B - if 0.4307 < z < 0.9674

A - if z > 0.9674