The difference between population and sample is easy to understand. Whether you are studying statistics in school or working as a statistician, you will be using the words population and sample often. Therefore, it is important to understand the meaning of these two words and the difference between them really well.
Suppose a statistician is trying to find out the following:
The population is the entire set of students, mothers, Toyota Camrys, or companies.
The population for the above examples is
As you can see, the word population does not refer to just people. It could refer to people or things such as books or cars.
In reality, you may never be able to get in touch with every single mother living in the USA or every single company around the world.
You may not even be able to contact half of all mothers or even one-tenth of all the companies around the world.
This is where sampling or taking a sample is important.
Since it is not always possible to get in touch with all members of a population, research is usually done with only a portion of the population.
For example, a study to find out how many mothers breastfeed their children could be performed with just a few thousand mothers.
In 2009, the estimated number of mothers in the United States was about 85 million.
Suppose you pick 10 thousand mothers to find out who breastfeed their children.
Suppose you want to know the prices of all Toyota Camrys sold in the USA. There is lots of data here since even if you focus on one single company, the prices may vary a lot.
Suppose that there 50,000 variations of the price and you pick 300 variations.
Of course, your population will have to be small in number. Say for instance a school has 5000 students.
5000 is your population.
With some good planning and organization, you may be able to get in touch with all the students in that population.