**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., :

Marks | 0-10 | 10-20 | 20-30 | 30-40 |

Number of Students | 2 | 5 | 2 | 1 |

**Inclusive Series:**Upper class limits of classes are included in the respective classes. E.g.,

Marks | 0-9 | 10-19 | 20-29 |

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.

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