Question

If class marks of a distribution are 10, 20, 30, 40, .......... find first and fifth class intervals.

Answer 1

Solution:-
There are certain rules to be remembered while constructing a grouped frequency distribution in this question.
1. The number of classes should be between 5 and 20.
2. If possible, the magnitude of the class must be 5 or multiple of 5.
3. Lower limit of the first class must be multiple of 5.
So, class interval would be like this:-
Class Interval
5 - 15                                     
15 - 25
25 - 35
35 - 45
45 - 55
And so on.....
As we know that a is the class mark and h is its class size, then lower limit and upper limit will be -
a - h/2 and a + h/2.
So, first class interval will be 5 - 15 and the fifth class interval will be
 45 - 55.

Answer 2

Solution:-

There are certain rules to be remembered while constructing a grouped frequency distribution in this question.

1. The number of classes should be between 5 and 20.

2. If possible, the magnitude of the class must be 5 or multiple of 5.

3. Lower limit of the first class must be multiple of 5.

So, class interval would be like this:-

Class Interval

5 - 15                                     

15 - 25

25 - 35

35 - 45

45 - 55

And so on.....

As we know that a is the class mark and h is its class size, then lower limit and upper limit will be -

a - h/2 and a + h/2.

So, first class interval will be 5 - 15 and the fifth class interval will be

 45 - 55.