Data is the information about facts or numbers collected to be examined and used to help with decisions. Data are the basic raw materials of statistics.
In statistics, data are classified into two broad categories: 1.Quantitative data and Qualitative data.
1. Quantitative data are those that can be quantified in definite units of measurement. These refer to characteristics whose successive measurements yield quantifiable observations. Eg. Age, income, number of firms etc
2. Qualitative data refer to qualitative characteristics of a subject or an object. A characteristic is qualitative in nature when its observations are defined and noted in terms of the presence or absence of a certain attribute in discrete numbers. These data are further classified as nominal and rank data. Eg. Gender, Community, honesty…
(i) Nominal data are the outcome of classification into two or more categories of items or units comprising a sample or a population according to some quality characteristic. Classification of students according to their sex (as males and females), Workers according to their skill (as skilled, semi-skilled, and unskilled), and of employees according to their level of education (as matriculates, undergraduates, and post-graduates).
(ii) Rank data, on the other hand, are the result of assigning ranks to specify order in terms of the integers 1,2,3, ..., n. Ranks may be assigned according to the level of performance in a test, a contest, a competition, an interview, or a show. The candidates appearing in an interview, for example, may be assigned ranks in integers ranging from I to n, depending on their performance in the interview.
Based on the data sources, data could be seen as of two types, viz., secondary data and primary data. The two can be defined as under:
(i) Primary data: Those data which do not already exist in any form, and thus have to be collected for the first time from the primary source(s). By their very nature, these data are fresh and first-time collected covering the whole population or a sample drawn from it
(ii) Secondary data: They already exist in some form: published or unpublished in an identifiable secondary source. They are, generally, available from published source(s), though not necessarily in the form actually required. Eg. Data from CSO, NSSO, RBI….