Under such series all the variables are divided in certain continuous groups and their respective frequencies will be written with them the following example will clear the form of such series.
Example:
| Marks |
0-5 |
5- 10 |
10 - 15 |
15 - 20 |
20 - 25 |
25 - 30 |
30 - 35 |
35 - 40 |
| No.of Students |
11 |
22 |
25 |
30 |
19 |
17 |
11 |
10 |
following are the elements of a continuous series:
1. Class Intervals:
These are the measurement which some problems is measured and written in continuous group. In the above example (0-5), (5-10) etc are the class intervals of the series.
2. Limits of class intervals:
Each class interval figure is known as limits of class interval. Small figures class intervals are known as lower limit class interval. In class interval (0-5) O is lower limit and 5 is a upper limit of tins class interval.
3. Magnitude of class intervals:
The difference between upper limit and lower limit of a class interval (0-5),5 is the magnitude.
4. Mid Value:
The average of two limits of the class interval is known as mid value e.g., the mid value of the class interval 0-5 will be 
= 2.5
5. Frequencies:
Number of repetition of items of various class intervals in the universe is known as frequencies which will be written with them.
Exclusive and Inclusive continuous series,
a. Exclusive series:
Where the value of upper limit is not included in the same group. But will be included in next group, it is known as exclusive series e.g.
| Class interval |
(0-10) |
(10 -20) |
(20 - 30) |
(30 - 40) |
(40 - 50) |
(50 - 60) |
| Frequency |
8 |
12 |
15 |
16 |
9 |
3 |
In the above series, 10, 20, 30, 40, 50 and 60 will not be included in first, second, third, fourth fifth and sixth group respectively.
b. Inclusive series:
Where values of upper limit is included in the same group, it is known as inclusive series e.g.
Class interval
|
(10-19) |
(20 -29) |
(30 - 39) |
(40 - 49) |
(50 - 59) |
| Frequency |
5 |
9 |
12 |
18 |
14 |
In the above series, value 19,29,39,49, 59 will be included in the same groups in which they are written, therefore, this series will be known as inclusive series.
