Simple random sampling is the most common method of sampling in research. This kind of sampling technique is possible when every unit of the population is accessible and known. As well as, the researcher has a list of all the elements of the population. The researcher need to have a list of all the elements of the population to use simple random sampling.
This is very basic in nature and therefore, it is the basis for many other complex type of random sampling. This makes simple random sampling a very important sampling technique. Once you know how to do this you can easily do systematic sampling or stratified sampling.
There is a standard procedure in simple random sampling that allows the researcher to draw unbiased sample from the population.
Fishbowl draw or lottery method
The easiest method is to number each element in the population, this works only if the population is small. Write down each number on a slip of paper and fold them so that the number is not visible. Then, the researcher selects a select number of slips randomly. This is called as drawing sample by lottery method. Alternatively, the researcher will place all the slips of paper in a bowl and draw random samples from it. This is called the Fishbowl draw method. But, the procedure is same in both ways.
Table of random numbers
A table of random numbers is often used to draw a simple random sample. The table of random numbers is usually a 4 to 5 page list of random numbers. They are present in most statistics books as well as you can find them online. There are a series of digits from 0 to 9 arranged in a random manner in these tables. The numbers are mostly 5-digit and they spread across rows and columns.
Let’s take an example to understand the use of table of random numbers. For example you have 500 students in a high school and you have to randomly select 25 students to participate in a survey. You have to assign a number from 1 to 500 to each student in the school. Now , as you have to select 25 students you have to use the table of random numbers in the following way.
- List all the students from 1 to 500, so that each student has an equal and fair chance of participation in the sample.
- Randomly select the first number from the table and move forward in your pre-determined direction to select the next number.
- Since, the maximum number is in three-digit, you have to select the first three digits from each entry in the table of random numbers. So for example if you landed on a number 34567, you will select 345.
- Now as 345 is smaller than 500 therefore it is possible to select this number, but if you landed on another number like, 76013. The first three digit of this number are 760 that are greater than 500 so you have to skip this number and move forward to the next randomly selected number.
- The selection procedure goes forward until you select your required 25 students form the table.
Table of random number
Another way is to use some computer-generated program to draw a random sample. There are many computer-generated program available today and they produce close to random sample but they are not as efficient as the manual table of random numbers. All of these programs meet close to true randomness but all of them vary in how efficient they are. Most of them generate pseudo-random–numbers which are not truly random.
Merits of random sampling
- Random sampling is the most basic method of random sampling and many more elaborate and complicated random sampling methods emerge from it.
- This sampling method gives equal and fair chance to every sampling unit in the population, therefore, it is highly suitable for empirical research.
- It produces highly generalizable, reproducible, and authentic sample.
- It helps the researcher eliminate the sampling bias from the research.
- Another merit of random sampling is its sheer simplicity which makes it very easy to use.