Statistics is a branch of mathematics where one studies data. The word data means information. This branch deals with collection, presentation, analysis and interpretation of numerical data. Statistics expresses data quantitatively not qualitatively.
Statistical data are of two types:
Primary Data: This type of data is collected by investigator himself with a definite plan. For example, data collected in population census are primary data. Primary data are relevant and reliable because they are original and are collected by some individual, research bodies or by some institutions.
Secondary Data: This type of data is not originally collected but obtained from published or unpublished sources. Secondary data are collected by some individual or research bodies and are used by someone else in another context. Therefore, it should be used with care.
After the collection of data, it is arranged in order to study their features. Such arrangement of data is called presentation. The raw data when arranged in ascending or descending order is called an array. Frequency distribution is another method of presenting raw data in the form from which one can easily obtain the information contained in the raw data. The more convincing and appealing way of presenting data is through graph and pictures. Bar graph, histogram, picture graph, pie graph are some of the methods to represent data.
After collecting and presenting data comes analysis and interpretation. Various methods are used for these jobs. Finding mean, mode, median, deviation, variance are some of the methods of studying the collected data and reach to a conclusion.
