Statistical Sampling

This is about statistical selecting a Random subset of a population. The statistical Sampling is defined has the collection of the subsets of the individuals of a similar likely hood.

There are many methods available for data collection. In this, the most important two methods are
(1)   Census Method
(2)   Statistical sampling

Non Statistical Sampling

 Non-Statistical or Non-probability sampling is a sampling procedure, which does not have any probability involved in it. All the items selected will be purposely selected for some reason.
 Important Non-probability Sampling methods are

(1)    Convenience Sampling
(2)    Quota Sampling
(3)    Judgment sampling
The non-statistical sampling methods are sometimes known as restricted sampling

Convenience Sampling: If a sample is selected from the convenient population, it is called convenience sampling. For example, to study some particular characteristics of college students, if we select a sample of students in the near by college the sample is called convenient sample.

Demerits

(1)    This method is sometimes biased
(2)    It may be unsatisfactory sometimes.


Quota Sampling: This method is adopted in making surveys of public opinions.  Only definite quotas of persons in different social classes, different age groups, regions etc are selected for the interview.


Judgment Sampling: Judgment sampling is also known as deliberate sampling or purposive sampling. In this method, the items as selected according to the investigators choice.  He picks up those items, which he thinks are the representative of the population. So under this method, the selection of the items to be included in the sample depends on the investigator and no formula or principle is followed.

Demerits

(1)    If the investigator is biased, the method will be a failure
(2)    This is not a scientific method.

Statistical vs Non Statistical Sampling

1. Statistical sampling is based on the probability of selecting each item where are non-statistical sampling does not have any probability involved in it.

2. In statistical sampling we can measure the errors of estimation and also it ensures the law of statistical regularity. In non-statistical sampling generally the person selecting the sample purposely selects a sample, which is suitable for his study. Hence error estimation cannot be done and the law of statistical regularity cannot be ensured.

3. Statistical sampling is known as unrestricted sampling and Non- statistical sampling is known as restricted sampling.