A sequence of observation, made on a set of objects included in the sample drawn from population is known as statistical data.
(1) Ungrouped Data:
Data which have been arranged in a systematic order are called raw data or ungrouped data.
(2) Grouped Data:
Data presented in the form of frequency distribution is called grouped data.
Collection of Data:
The first step in any enquiry (investigation) is collection of data. The data may be collected for the whole population or for a sample only. It is mostly collected on sample basis. Collection of data is very difficult job. The enumerator or investigator is the well trained person who collects the statistical data. The respondents (information) are the persons whom the information is collected.
Types of Data:
There are two types (sources) for the collection of data.
(1) Primary Data (2) Secondary Data
(1) Primary Data:
The primary data are the first hand information collected, compiled and published by organization for some purpose. They are most original data in character and have not undergone any sort of statistical treatment.
Example: Population census reports are primary data because these are collected, complied and published by the population census organization.
(2) Secondary Data:
The secondary data are the second hand information which are already collected by some one (organization) for some purpose and are available for the present study. The secondary data are not pure in character and have undergone some treatment at least once.
Example: Economics survey of England is secondary data because these are collected by more than one organization like Bureau of statistics, Board of Revenue, the Banks etc…
Methods of Collecting Primary Data:
Primary data are collected by the following methods:
Methods of Collecting Secondary Data:
The secondary data are collected by the following sources:
Official: e.g. The publications of the Statistical Division, Ministry of Finance, the Federal Bureaus of Statistics, Ministries of Food, Agriculture, Industry, Labor etc…
Semi-Official: e.g. State Bank, Railway Board, Central Cotton Committee, Boards of Economic Enquiry etc…
Difference between Primary and Secondary Data:
The difference between primary and secondary data is only a change of hand. The primary data are the first hand data information which is directly collected form one source. They are most original data in character and have not undergone any sort of statistical treatment while the secondary data are obtained from some other sources or agencies. They are not pure in character and have undergone some treatment at least once.
For Example: Suppose we interested to find the average age of MS students. We collect the age’s data by two methods; either by directly collecting from each student himself personally or getting their ages from the university record. The data collected by the direct personal investigation is called primary data and the data obtained from the university record is called secondary data.
Editing of Data:
After collecting the data either from primary or secondary source, the next step is its editing. Editing means the examination of collected data to discover any error and mistake before presenting it. It has to be decided before hand what degree of accuracy is wanted and what extent of errors can be tolerated in the inquiry. The editing of secondary data is simpler than that of primary data.