Distribution of grades
A=upper 10%
B=next 20%
C=next 50%
D=next 15%
F=lowest 5%
The class (population average) is 923 with a standard deviation of 101. Determine the number of points needed for each letter grade.

Question

Distribution of grades
A=upper 10%
B=next 20%
C=next 50%
D=next 15%
F=lowest 5%
The class (population average) is 923 with a standard deviation of 101. Determine the number of points needed for each letter grade.

anonymous · Answer

At first I converted the percentages to decimals and then used that as my Z value =(x-mean)/st. dev. but it doesn't seem quite right to me.

anonymous · Answer

I think look up the Z value for 5%, 15%... and the  convert it from the standard normal with the mean and sd.

anonymous · Answer

Assuming you have a CDF lookup table or some other means.

anonymous · Answer

what is the answer can i check if you got it right or no

anonymous · Answer

@amorable

anonymous · Answer

Hold on and I'll post. I want to try and redo it real quick

anonymous · Answer

I tried it a different way than I had originally and got the minimum D value of 761.4

anonymous · Answer

the real answer is 11% so it is A

anonymous · Answer

I'm not sure I follow. I'm suppose to find the range of points needed to get each letter grade.