The Following Is a Frequency Distribution of Grades of a Sample

Short Answer

The following is a frequency distribution of grades of a sample of statistics examinations.
$$\begin{array} { c c } \text { grade } & \text { Frequency } \\50 - 59 & 7 \\60 - 69 & 10 \\70 - 79 & 22 \\80 - 89 & 15 \\90 - 99 & 6\end{array}$$ Compute the following measures:
a. The mean
b. The variance
c. The standard deviation
d. The coefficient of variation