Census and Sample : Under the census data are collected for each and every unit of population on the other side sampling is simply the process of learning about the population on the basis of a sample
The sampling can be grouped under two broad heads probability sample and non probability sample. where as probability sampling method are those in which every item in the universe has probability of being chosen for the sample. where as non-probability sampling method are those which do not provide every item in the universe with a known chance of being included in the sample.
1. Probability Sampling Method
(a) Sample Random Sampling: Lottery Method, Table of Random Number
(b) Systematic Sampling: In it the first sample is selected randomely and generally followed by Kth students
K=N/n
K= Sampling Interval , N=Universe Size and n= Sample Size
for example in a class 100 students with roll no from 1 to 100. It is decided to take a sample of 10 students. Use systematic sampling method
Now,
K=N/n
100/10=10
Suppose the first student comes out to be 6th
6, 16, 26, 36, 46, 56, 66, 76, 86, 96
(c) Cluster Sampling: There are several stages in which the sampling process is carried out. Suppose we want to take a sample of 5000 households from the state of U.P . At the first stage, the state may be divided into a number of districts and a few districts selected at random. At second stage each district may be sub divided into number of villages and sample of villages may be taken at random. At third stage a number of household may be selected from each of villages selected at second stage.
2. Non-Probability Sampling
(a) Judgement Sampling: In this method of sampling the choice of sample items depends exclusively on the judgement of the investigator. In other words the investigator select the sample on the basis of his or her own judgement.
(b) Quota Sampling: The quota sampling is type of judgement sampling and is perhaps the most commonly used sampling techniques in non-probability category. In the quota sample quotas are set up according to some specified characteristics such as so many in each of several income groups, so many in each age, etc.
(c) Convenience Sampling: The sample which is easily available such as telephone directory etc