Grouped Data
We can divide data into groups. Such a presentation is called grouped data. The groups are known as classes or class intervals.
The above data can be presented as follows in the from of grouped data.
Heights (cms) |
Frequency |
156 - 160 |
4 |
161 - 165 |
9 |
166 - 170 |
6 |
171 - 175 |
5 |
176 - 180 |
1 |
We have grouped the data in various class intervals. These class intervals are non-over lapping.
The class 156-160 means that the height of employees lies between 156 cm and 160 cms. (including 156 and 160).
The number of observations falling in a particular class is known as the frequency of that class.
Thus the frequency of class 156 - 160 is 4 and the class 161 - 165 has 9 as class frequency and so on.
156 is called the lower limit of class 156 - 160 and 160 is called upper limit of the class.
The class intervals 156 - 160 is called first class interval. Class interval 161 - 165 is called second class interval. Class interval 176 - 180 is called fifth class interval.
This type of presentation of data is called grouped frequency distribution.