Coefficient of Variation

I am not sure whether the class average is relative or not in this question.

Mr. T received a grade of 82 in chemistry in which the class average was 68 and the standard deviation was 8. On an economics exam, he received a grade of 89 in the class, and the class average was 80 with a standard deviation of 6. In which subject is Mr. T's relative performance higher?

I calculated the CV by just using the S.D. and MR. T's score in both chemistry which i got 0.098 and economics which i got 0.067 but i am not sure if i did it right or not. Please help and thanks in advance.

Compare the z-scores:

For the chemistry exam:

\(\displaystyle z=\frac{82-68}{8}=\frac{7}{4}\)

For the economics exam:

\(\displaystyle z=\frac{89-80}{6}=\frac{3}{2}\)

For the chemistry he is 1.75 standard deviations above the mean.

On the economics, he is 1.5 standard deviations above the mean.

Which is better?.