Each of the successive intervals in which is divided the total interval of variation of a quantitative statistical variable.
The size of these intervals is called the amplitude of the statistical class.
Example
Mass of 190 students at school | |
Mass (in kg) |
Numbers of students |
[36, 38[ [38, 40[ [40, 42[ [42, 44[ [44, 46[ [46, 48[ [48, 50[ [50, 52[ |
14 20 25 35 44 32 15 5 |
Total | 190 |
Based on this table, we grouped the data into 8 classes.
The amplitude or dimension, or range) of each class is 2.
For the class [36, 38[, the lower bound is 36 and the upper bound is 38.
The frequency of the class [36, 38[ is 14.
The range of the distribution is 23, because: E = 52 − 36 = 23.