In the singular sense, statistics refers to the methods and principles of  (i). Collection of data  (ii). Presentation of data.  (iii). Analysis of data, and  (iv). Interpretation of data.

(i) Collection of data :

Collection of data forms the beginning of any statistical stud or enquiry. At the outset a researcher identifies the problem and then he collects data on that problem. He can collect the data in two ways. First, data can be collected from the original source. Such information are called ‘primary data’. Second, he can also gather the same information from some secondary source. These are called ‘secondary data.’

(ii) Presentation of data :

Data which are collected by the researcher from the primary source for the first time are Raw data. Raw data are like raw materials. As such they do not convey any meaning. So after collection, information should be organized and presented properly. Presentation of data is essential for their analysis Generally, data are presented in terms of tables or by using graphs or diagrams. That gives tabular, graphs or diagrammatic presentation of data.

(iii) Analysis of data :

Valid conclusions are derived by carefully analyzing the data. For analysis data must be arranged in groups or classes according to some similarities or resemblances. This is known as ‘classification of data’. Classification makes the analysis simple and intelligible. For this, it is said, “classification and arranged facts speak for themselves. Unarranged, they are as dead as mutton”.

(iv) Interpretation of data :