Question

The following are the marks obtained in Maths by students of Class 8:
51, 94, 34, 20, 50, 81, 81, 90, 76, 34, 51, 86, 93, 99, 26, 54, 85, 71, 88, 40, 44, 56, 55, 57, 78, 53, 81, 78, 65, 78.
The data have to be grouped to find the mean marks.
One of the class intervals made is 60-70.
How many should such class intervals be prepared?
What is the frequency of the last class interval?
What is $\sum f_i$ ?

• A. 8, 4, 28
• B. 8, 4 , 30
• C. 10, 1, 30
• D. 10, 4, 30

Answer 1

The correct option is B

8, 4 , 30

$\begin{array}{cc}Classinterval& Frequency\left(f_i\right)\\ 20-30& 2\\ 30-40& 2\\ 40-50& 2\\ 50-60& 8\\ 60-70& 1\\ 70-80& 5\\ 80-90& 6\\ 90-100& 4\\ & \sum f_i=30\end{array}$
From the frequency distribution table, one can infer that,

The number of class intervals to be prepared is = 8
The frequency of the last class interval is = 4
$\sum f_i$ = 30