Population and sample

The population is the whole set of the elements that is the object of our statistical study.

When the population is very numerous or inaccessible, we extract a sample or a subset of the whole population. The number of elements of the sample, N, is called size.

An individual is each element of the population or sample.

For example, if we want to do a study about the pet that people from Illescas prefer and we are going to ask 100 people, the population is the people from Illescas, the sample is those 100 people we will ask and the size is 100. An individual is each inhabitant of the city.