The quantity whose different values during observation constitute the collection of data is called a statistical variable.
In collection A, the marks obtained by the students is a variable. If we denote the marks obtained by x then x is a variable in the collection.
A variable can be of two types.
(i) Discrete variable: A variable which can assume only a finite number of values between two given values is called a discrete variable.
For Example: If x students for marks obtained then x is a discrete variable for collection A because x takes only integral values from 4 to 90.
(ii) Continuous Variable: A variable which can assume all real values between two given values is called a continuous variable.
For Example: The height and the weight of a person are continuous variables.
Note: We will deal mostly which discrete variables.