Data Collection:
Collection of data is the first and most important statistical investigation. The process of collecting necessary information from the field of inquiry by the investigators themselves or by their agents is called data collection. If the collected data are reliable, then the decision will be correct. Otherwise, the results will be misleading and may be harmful also.
Sources of Data:
On the basis of sources of data, there are two types of data:
- Primary data: The data which are collected by an investigator originally from its basic source for the first time for any statistical inquiry are known as primary data. The primary data are also called first-hand data. As it is collected directly from the informants. Primary data are generally used in those cases where the secondary data do not provide an adequate basis for analysis. Primary data are also called field source. Example: Data obtained in a population census by C.B.S (Central Bureau of statistics) are primary data of the same organization.
- Secondary data: Those data which are collected by one agency organization or person but used by other agency, organization or person is called secondary data. These types of data are not original for the user. These are also called second-hand data. The data which are already collected by someone but obtained from some published and unpublished sources are called secondary data. Example: For Central Bureau of statistics, the census data are primary whereas, for all others we use, such data are secondary.
Differences Between Primary and Secondary Data:
| Primary data | Secondary data |
| Data collected the first time from the field of study are called primary data. | Data that are already collected and used by others are called secondary data. |
| They are first hand or original in nature. | They are second hand in nature. |
| It gives more accurate information. | Sometimes secondary data may not be accurate. |
| They are like raw materials and they have to be processed after collection. | They are found in ready-made form just like finished goods. |
| Collection of primary data takes a large amount of money and efforts. | Secondary data save money, time and efforts because these are used from the existing sources. |
| There is no need to worry about while using primary data from the investigator. | Secondary data should be carefully and critically examined before they are used. |
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