Classification of Data: The process of grouping data according to their characteristics is known as classification of data.
Objectives of Classification:
- To simplify complex data: The main objective of classification is to condense the large data to make them easily understood.
- To facilitate understanding
- To facilitate comparison
- To make analysis and interpretation easy.
- To arrange and put the data according to their common characteristics.
Statistical Series: Systematic arrangement of statistical data
- Can be on the basis of individual units :
The data can be individually presented in two forms:
i] Raw data: Data collected in original form.
ii] Individual Series: The arrangement of raw data individually. It can be expressed in two ways.
- Alphabetical arrangement : Alphabetical order
- Array: Ascending or descending order.
- Can be on the basis of Frequency Distribution:
Frequency distribution refers to a table in which observed values of a variable are classified according to their numerical magnitude.
- Discrete Series: A variable is called discrete if the variable can take only some particular values.
- Continuous Series: A variable is called continuous if it can take any value in a given range. In constructing continuous series we come across terms like:
- Class : Each given internal is called a class e.g., 0-5, 5-10.
- Class limit: There are two limits upper limit and lower limit.
- Class interval: Difference between upper limit and lower limit.
- Range: Difference between upper limit and lower limit.
- Mid-point or Mid Value: Upper limit – Lower limit 2
- Frequency: Number of items [observations] falling within a particular class.
- Exclusive Series: Excluding the upper limit of these classes, all the items of the class are included in the class itself. E.g., :
|Number of Students||2||5||2||1|
- Inclusive Series: Upper class limits of classes are included in the respective classes. E.g.,
|Number of Students||2||5||2|
- Open End Classes : The lower limit of the first class and upper limit of the last class are not given. E.g.,
|Marks||Below 20||20-30||30-40||40-50||50 and above|
|Number of Students||7||6||12||5||3|
- Cumulative Frequency Series: It is obtained by successively adding the frequencies of the values of the classes according to a certain law.
- Less than’ Cumulative Frequency Distribution : The frequencies of each class-internal are added successively.
- More than’ Cumulative Frequency Distribution: The more than cumulative frequency is obtained by finding the cumulative totals of frequencies starting from the highest value of the variable to the lowest value.