Statics is that branch of mathematic which deals with the collection, classification, representation, analysis and interpretation on numerical data.
The study of statistics started nearly 2000 years ago. Today statistics holds an important place in the fields of economics, business, industry and in all branches of science. Prominent among those who applied statistics in different branches of science are Galton (1822 – 1921), Karl Pearson (1857 – 1936) and R A Fisher (1890 – 1962). Among Indian statisticians Prof. P C Mahalanobis Holds an important place.
Statistical study begins with collecting data. Based on the method of collection, data may be classified into two categories.
(i) Primary Data: If the investigator collects the data by personal observation and is solely responsible for their correctness then the data are called primary data.
(ii) Secondary Data: If the investigator prepares the data based on information provided by different sources such as correspondence or publications then the data are called secondary data.
Sample or Representative Data:
If the field of study is not very large then we can collect all the relevant data. But if it is very large then we use samples.
For Example: If we have to study the health of 5,000 people of a block, we can select 500 people on some basis and after studying their health we can make inference about the health of the people of the block. Here, only 500 people represent the whole collection of 5,000 people.