The number of phone calls arriving at a switchboard each hour has been recorded, and the following frequency distribution has been developed.
$$\begin{array} { l c }
\text { Class Interval } & \text { Frequency } \
20 \text {-under } 40 & 30 \
40 \text {-under } 60 & 45 \
60 \text {-under } 80 & 80 \
80 \text {-under } 100 & 45
\end{array}$$
What is the midpoint of the last class?
A)80
B)100
C)95
D)90
E)85

Question

The number of phone calls arriving at a switchboard each hour has been recorded, and the following frequency distribution has been developed. 
$$\begin{array} { l c } 
\text { Class Interval } & \text { Frequency } \
20 \text {-under } 40 & 30 \
40 \text {-under } 60 & 45 \
60 \text {-under } 80 & 80 \
80 \text {-under } 100 & 45
\end{array}$$
What is the midpoint of the last class?
A)80
B)100
C)95
D)90
E)85

Quizplus · Accepted Answer

The midpoint of a class interval is calculated by averaging the lower and upper boundaries of the class. For the last class (80-under 100), the midpoint is (80 + 100) / 2 = 90.

The Number of Phone Calls Arriving at a Switchboard Each