Simple random sampling

What is simple random sampling?

Simple random sampling is a type of probability sampling in which all elements of the population have the same probability of being selected.

This system works through a "lottery" method between a universe of individuals, in which each member is assigned a number to be chosen.

For example, if a sample of 50 people needs to be selected from a universe of 1000, those 1000 people will be assigned a number and, as a lottery, 50 numbers will be randomly selected to make up the required sample.

Said procedure guarantees that all sample elements have the same probability of being selected to be part of the sample.

Random selection of simple random sampling.

Advantages and disadvantages of simple random sampling

Simple random sampling has both advantages and disadvantages.

Advantage

The advantages of simple random sampling are as follows:

• It is simple to assemble the samples.
• Take the selection fairly of samples from a population.
• In general, all individuals of the population they have an equal chance of being selected.
• The population is representative, the only margin of error being luck, called sampling error.
• Is he best method when explaining the results, since its selection is random and impartial.
• Due to the representativeness obtained generalizations can be made regarding the population, from the results of the samples.

Disadvantages

The disadvantages of simple random sampling are as follows:

• A complete list is required of all members of the population.
• She is ready must be properly prepared, complete and updated.
• In large populations it's hard have the necessary data for this type of sampling, so it is recommended to use another technique.

Examples of simple random sampling

Let's look at the following example: a consulting firm that performs audits on various organizations decides to conduct an investigation in a company where 500 employees work.

To carry out this study, the consulting firm must work on a statistical sample of 50 people (10%), so he chooses to use the simple random sampling method, for which he follows the following steps:

1. List with number the 500 employees of the organization.
2. Choose 50 numbers at random.
3. Finally, those 50 numbers that correspond to an employee will be the individuals that make up the sample.

In this way, the sample will be formed to carry out the investigation, having granted, to all the employees of the organization, the same chances of being selected.