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 are the upper and the lower limits of the first class interval?
What is $\sum f_i$ ?

• A. 8, 4, 20, 30, 28
• B. 8, 4, 30, 20, 30
• C. 10, 1, 0, 10, 30
• D. 10, 4, 10, 0, 30

Answer 1

The correct option is B 8, 4, 30, 20, 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
The upper and the lower limits of the first class interval are 30 and 20 respectively.
And, the $\sum f_i$ is = 30