**Population** It refers to the universe, set or totality of elements on which research or studies are carried out. **Sample** It is a part or subset of elements that are previously selected from a population to carry out a study.

Normally a sample of a population is selected for study, because studying all the elements of a population would be very extensive and impractical.

Population Sample Definition Universe of elements to be studied. Selection of a part of the population that is going to be the subject of study. Characteristics It can be classified according to the number of individuals that make it up. It has statistical variables. It is part of the population: it should comprise between 5% and 10% to be most effective. Items must be random. It must be representative of the population. Objectives Analyze the data collected regarding the common characteristics shared by the elements with different purposes. Study the behavior, characteristics, tastes or properties of a representative part of the population. Examples The people who inhabit a country. The number of cars in a city. students of a country.

To study the performance of students from five universities in a city in a specific subject, 500 students are randomly taken as a sample (100 from each institution) who are studying the same level so that the sample is representative.

## What is population?

The statistical population, also known as the universe, is the set or the **totality of elements** that they are going to study.

The elements of a population are made up of each of the associated individuals, because **share some characteristic in common**.

The statistical population can be a set of real people, places, or things. For example, the adolescents of a town or the possible uses of sugar in cooking recipes.

As it is very difficult to carry out a study with all the elements that make up a population, especially if it is considered an infinite population, a representative sample is taken from it to carry out the studies.

### Types of populations

The population can be classified as follows according to the number of individuals that make it up:

**finite population**: is one that can be counted and its members can be studied more easily. For example, the number of people enrolled in a gym.

**infinite population**: they are huge populations where it is very difficult to count their members, so only a portion of it is usually taken into account when conducting a study, thus selecting a sample. For example, the number of grains of sand on a beach.

**actual population**: are groups of tangible members. For example, the number of animals in a zoo.

**hypothetical population**: are possible populations that can be studied in the event of an eventuality. For example, the number of premature births.

## What is sample?

The sample is a **representative part of a population** where its elements share common or similar characteristics.

It is used to study the population in a more **feasible**, because it can be accounted for easily. When a study is going to be carried out on the behavior, properties or tastes of the total of a specific population, samples are usually taken.

These studies that are carried out on the samples serve to create norms or guidelines that will allow taking actions or simply knowing more about the studied population.

He **sampling** It is a research tool that, when used properly, allows specific conclusions to be drawn and avoids biased results.

The main advantages of using the samples is the reduction of costs, since it reduces the elements to be studied and can be carried out in less time.

The most important factors in sampling are the **representativeness**so that the elements possess common qualities according to the purpose, and the **randomness** when selecting the elements to avoid a flawed sample.

### Sample types

There are different types of techniques to form a sample.

#### random sampling

It is a technique that offers the same possibility to the elements of being selected, because they are taken at random. The types of random sampling are:

**simple random sampling**: Items are chosen from a random list. It works most effectively when the universe is small and homogeneous.

**Systematic sampling:** the first element is chosen at random and then the remaining elements are chosen at constant intervals.

**stratified sampling**: It is carried out by dividing the population into parts or strata that respond to established characteristics and then the individuals to be studied are randomly chosen.

**cluster sampling**: the population is divided into heterogeneous groups and these in turn are subdivided into homogeneous groups with common characteristics to be studied according to what is required by the researcher.

#### Sampling not random or by intentional selection

It is chosen based on the information management of the elements to be studied, so the representativeness of the sample can be subjective. In this case, there is a risk that the results will be biased.

When only one of the studies is not enough because the population to be studied is very large, two or more types of sampling can be used.

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