) units is N − and so on. . Several methods have been adopted for random selection of the samples from the population. Of those, the following two methods are generally used and which are described below.
(A) Lottery method This is the most popular and simplest method when the population is finite. In this method, all the items of the population are numbered on separate slips of paper of same size, shape and colour. They are folded and placed in a container and shuffled thoroughly. Then the required numbers of slips are selected for the desired sample size.
The selection of items thus depends on chance. For example, if we want to select students, out of students, then we must write the names/roll number of all the students on slips of the same size and mix them, then we make a blindfold selection of students. This method is called unrestricted random sampling, because units are selected from the population without any restriction. This method is mostly used in lottery draws.
If the population or universe is infinite, this method is inapplicable. (B) Table of Random number When the population size is large, it is difficult to number all the items on separate slips of paper of same size, shape and colour. The alternative method is that of using the table of random numbers. The most practical, easy and inexpensive method of selecting a random XII Std - Business Maths & Stat EM Chapter - - One may question, as to how it is ensured that these digits are random.
It may be pointed out that the digits in the table were chosen horizontally but the real guarantee of their randomness lies in practical tests. Tippett’s numbers have been subjected to numerous tests and used in many investigations and their randomness has been very well established for all practical purposes. An example to illustrate how Tippett’s table of random numbers may be used is given below. Suppose we have to select items out of , .
The procedure is to number all