Elementary Statistics and Computer Application

Sampling

• The method of selecting samples from a population is known as sampling.

Sampling technique
There are two ways in which the information is collected during statistical survey. They are

• Census survey
• Sampling survey

Census

• It is also known as population survey and complete enumeration survey. Under census survey the information are collected from each and every unit of the population or universe.

Sample survey

• A sample is a part of the population. Information are collected from only a few units of a population and not from all the units. Such a survey is known as sample survey.
• Sampling technique is universal in nature, consciously or unconsciously it is adopted in every day life.
For eg.

1. A handful of rice is examined before buying a sack.
2. We taste one or two fruits before buying a bunch of grapes.
3. To measure root length of plants only a portion of plants are selected from a plot.

Need for sampling

• The sampling methods have been extensively used for a variety of purposes and in great diversity of situations.
• In practice it may not be possible to collected information on all units of a population due to various reasons such as
1. Lack of resources in terms of money, personnel and equipment.
2. The experimentation may be destructive in nature. Eg- finding out the germination percentage of seed material or in evaluating the efficiency of an insecticide the experimentation is destructive.
3. The data may be wasteful if they are not collected within a time limit. The census survey will take longer time as compared to the sample survey. Hence for getting quick results sampling is preferred. Moreover a sample survey will be less costly than complete enumeration.
4. Sampling remains the only way when population contains infinitely many number of units.
5. Greater accuracy.