Brief notes on Random Sampling method as studied in Statistics

Simple Random Sampling. This method of sampling is also known as the Probability method’ or the method of ‘Chance selection’.

Under this method the various items of the sample are selected from the universe purely on a chance basis. As such, under this method of selection, each and every item of the universe has the equal chance of being included in the sample.

In the words of W.H. Harper, “A random sample is a sample selected in such a way that every item in the population has an equal chance of being included.”

According to C.H. Mayer, “A sample is said to be random when each unit has a probability identical to the probability of all other units which m^; have been drawn in its place.”

In the words of Simpson and Kafka, “Random samples are characterized the way in which they are selected. ‘Random’ is not used in the sense haphazard or ‘hit or miss”.

A random sample is one where each item in the universe has an equal or knows opportunity of being selected.”

Simple Random sampling may be done in any one of the following ways:

Lottery Method:

According to this method paper slips are made for each item the universe. These slips are shuffled in a box. Then, impartially, some of the slips drew to form a sample of the universe.

Example:

Suppose from a village of 60 cultivators we choose a sample of cultivators. In the lottery method, we give one rank each to 60 cultivators. Now, these 60 chits are mixed and 6 chits are drawn. The number of cultivators bearing the num of these selected chits will be taken as a sample.

Random Number Tables:

These tables are constructed in such a way that various digits from 0 to n appear with approximately the same frequency and independently each other.

Example.

If a sample of 200 units out of 2000 units is to be chosen, the first 2 numbers which appear row wise or column wise up to a value of 2000 will constitute the sample.