In statistics, the first approach for collecting data is called the Census Method and the second is called the Sample Method.
Universe or population simply refers to an aggregate of items to be studied for an investigation. Here are the notes of the census and sample method of collection of data.
Topics Discussed
Census Method
The census method is the method in which data are collected covering every item of the universe or population relating to the problem under investigation.
Suitability of the Census Method
- The small size of the population
- Widely diverse items in the population
- The high degree of accuracy and reliability
- Requirement of intensive examination of different items
Merits and Demerits of Census Method
| Merits | Demerits |
| Reliable and Accurate | Costly |
| Study of diverse characteristics | Not Suitable for large investigation |
| Indirect investigation | Large manpower |
Sample Method
The sampling method is the method in which data is collected about the sample on a group of items taken from the population for examination and conclusions are drawn on their basis.
For example: By examining only a few drops of blood, a doctor determines the blood group of a person.
Suitability of the Sampling Method
- The size of the population is very large
- Very high degree of accuracy is not needed
- An intensive examination of diverse items is not required
- When different units of the universe are broadly similar to each other
Merits and Demerits of the Sampling Method
| Merits | Demerits |
| Economical and more scientific | Partial investigation |
| Time-saving | Difficulty in framing a sample |
| Identification of error | Wrong conclusions |
Methods of Sampling
There are mainly 6 methods of sampling:
- Random Sampling
- Stratified Sampling
- Quota Sampling
- Purposive Sampling
- Systematic Sampling
- Convenience Sampling
Random Sampling
Random sampling is a method of sampling in which every item of the universe has an equal chance of being selected in the sample.
It may be done in any of the following ways:
- Lottery Method: In this method, paper slips are made for each item of the universe. These slips are shuffled in a box. Then impartially, some of the slips are drawn to form a sample of the universe.
- Tables of Random Numbers: Some statisticians have prepared a set of tables called Tables of Random Numbers. A sample is framed concerning these tables.
Purposive Deliberate Sampling
Purposive sampling is a method in which the investigator himself makes the choice of the sample items which in his opinion are the best representative of the universe.
Stratified or Mixed Sampling
According to this method of sampling, the population is divided into different strata having different characteristics, and some of the items are selected from each other strata so that the entire population is representative.
It is also called the mixed technique of sampling because this method involves a mixture of both purposive and random sampling.
Systematic Sampling
According to this method, units of the population are numerically, geographically, and alphabetically arranged. Every nth item of the numerical items is selected as a sample item.
Quota Sampling
In this method, the population is divided into different groups or classes according to different characteristics of the population.
This method of sampling is not very expensive but there is a high possibility of personal bias at the time of selection of the items by the investigator.
Convenience Sampling
In this method, sampling is done by the investigator in such a manner that suits his convenience. This method is the simplest and least expensive, but unscientific and unreliable. It depends too much on the whims of enumerators.
Tabular Presentation of Data Class 11 Notes
Difference between the Census Method and Sampling Method
| Basis | Census Method | Sampling Method |
| Coverage | In the census technique, an investigator collects information relating to all the items in the population. | In the sampling method, only some of the items are covered for an investigation. |
| Suitability | This method is suitable when the area of investigation is relatively small. | This method is suitable when the area of investigation is large. |
| Cost | This method is more expensive. | This method is less expensive. |
| Time | The census method is time-consuming. | The sampling method is less time-consuming. |
| Nature of Items | The census method is particularly suitable when the items in the population have diverse characteristics. | The sampling method is suitable when the items in the population are homogenous. |
| Accuracy | There is generally a greater degree of accuracy in the results based on the census method. | There is less accuracy and reliability in the sampling method. |