Sampling in statistics is the process of selecting the small part of population units(samples).Technique of drawing the representative portion of the entire population. sampling technique is the integral part of the research methodology. The main aim of is the selection of the true representative sample from the population.
Main Objectives of sampling in statistics
The main objective of sampling in statistics is to select the truly representative sample from the population. However, the following are the common objectives are:
- To obtain maximum information about the population.
- To ascertain confidence interval to the estimate of population parameter.
- To test the significance of the population parameters at the given level of significance.
Why there is a need for sampling in statistics?
- If complete enumeration is not possible, then the selection of the sample is an appropriate and essential task of the investigation.
- This can save time and money.
- It may be the only way for studying the universe having infinitely many members.
- It may be the only choice if the test involves the destruction of the item under investigation.
- It is very useful technique to arrive at a conclusion on population parameters in a short period of time and in less expense.
- It enables to estimate sampling error, by using which we can predict the result in a desired level of precision.
- It may provide more accurate measurements if it is conducted by well trained and experienced persons.
- It enhances the better quality of data.
What is sampling unit in statistics?
The population units selected in the samples are called sampling units. Types of units dealt in socio-economic surveys are;
- Geographical units: Ecological regions, districts, wards etc.
- Structural units: a house, a flat, a resident etc.
- Social group units: a family, a school, a club etc.
- Individuals: a person, an item etc.
Sampling frame definition in research?
- Sampling frame is a list of population units having same characteristics from which the sample units are drawn.
- It is also called sampling list.
- If frame is not available then it should be prepared before conducting the main survey.
- It is available in CBS or in respective administrative office.
Essential qualities of a Sampling frame
- It should be exhaustive.
- It should be up to date.
- It should contain sufficient(full) information.
- The unit must not be repeated.
- The list should be suitable for the coverage of the study.
What is the Use of sampling in statistics? with example:
- The technique is used to estimate the values of unknown population parameters.
- It is commonly used in hypothesis testing.
- It is also used in our daily life.
- For example:
- A house wife generally tests very small quantity of cooking food to know about the test of whole food that she is cooking.
- A doctor tests a drop of blood of a patient to know about the characteristics of the whole blood of the patient.
- Shoppers often sample a small piece of cheese before purchasing any etc.
What are Advantages and disadvantages of Sampling in statistics
Advantages of sampling
- Reduce cost.
- Greater speed.
- Greater scope.
- Greater accuracy.
- Mandatory in some cases.
- Saves destruction etc.
Disadvantages of sampling
- Chances of bias
- Difficulties in selecting truly a representative sample.
- Need for subject specific knowledge.
- changeability of sampling units.
- If the population size is very small then the this technique is not preferred.