The types of hypothesis of scientific research are the null hypothesis, the general or theoretical hypotheses, the working hypotheses and the alternative hypotheses. A hypothesis determines the possible characteristics of the variables and the relationships that exist between these variables.

During a scientific investigation, an attempt will be made to demonstrate the validity of a main hypothesis. This is known as a working hypothesis. If it is desired to investigate several plausible hypotheses, alternative hypotheses will be considered. Within the working hypothesis and the alternatives there are three subtypes: attributive, associative and causal hypothesis.

Unlike working and alternative hypotheses, which quantify the relationship between variables, general or theoretical hypotheses establish a conceptual relationship between them. On the other hand, there is also the null hypothesis, which is what determines that there is no relevant relationship between the variables under study.

If the validity of the working hypothesis and alternative hypotheses can not be proved, the null hypothesis will be accepted as valid. In addition to these, there are other types of hypotheses, such as relative and conditional ones. They can also be classified according to other criteria; for example, it is possible to distinguish between probabilistic and deterministic hypotheses.

## Index

- 1 .- What is the hypothesis of scientific research?
- 2 .- The 4 types of main hypothesis in a scientific investigation
- 2.1 1.- Null hypothesis
- 2.2 2.- General or theoretical hypotheses
- 2.3 3.- Work hypothesis
- 2.4 4.- Alternative hypotheses
- 3.- Other types of hypothesis
- 3.1.- Relative hypotheses
- 3.2.- Conditional hypotheses
- 4.- Possible alternative classifications
- 4.1.- Probabilistic hypotheses
- 4.2.- Deterministic hypotheses
- 5.- references

### What is a scientific research hypothesis?

All scientific research must start from one or several hypotheses that are intended to be demonstrated.

A hypothesis is an assumption that can be verified by scientific research. In other words, the hypotheses are the formulation of the problem: they establish possible relationships between variables.

There are many different ways to classify hypotheses according to different criteria. The most common is that which distinguishes between null hypotheses, general or theoretical hypotheses, working hypotheses and alternative hypotheses. In turn, within each category different subtypes are identified.

### The 4 types of hypothesis of a scientific investigation

#### 1- Null hypothesis

The null hypothesis assumes that there is no relationship between the study variables. For this reason, it is also known as a non-relationship hypothesis.

This hypothesis will be accepted if the research shows that the working hypothesis and alternative hypotheses are not valid.

Example

“There is no relationship between students’ hair color and their academic results.”

#### 2- General or theoretical hypotheses

The general or theoretical hypotheses are those that are formulated in a conceptual way, without quantifying the variables.

Normally, these hypotheses are obtained through a process of induction or generalization based on the observation of similar behaviors.

Example

“The more hours a student studies, the better grades he gets.”

Among the theoretical hypotheses are the difference hypotheses, which are those that determine that there is a difference between two variables but do not measure their magnitude. For example, “in the university, the number of national students is greater than the number of international students”.

#### 3- Work hypothesis

The working hypothesis is the one that must be demonstrated or supported through scientific research.

These hypotheses can be verified experimentally, so they are also called operational hypotheses.

In general, they are obtained from the deduction: they are based on general laws that are particularized in a specific case. The working hypotheses can be attributive, associative or causal.

- – Attributable

The attributive hypothesis or point prevalence describes the facts. This hypothesis is used to describe real behaviors, which are measurable and can be distinguished from other behaviors. The attributive hypothesis is composed of a single variable.

Example

“The majority of university students are between 18 and 23 years old.”

- – Associative

The associative hypothesis establishes a relationship between two variables. If the first variable is known, it is possible to predict the second.

Example

“There are twice as many students in the first course as in the last one.”

- – Causal

The causal hypothesis determines a relationship between two variables. The increase or decrease of the first variable determines an increase or decrease in the second variable. These variables are called “cause” and “effect,” respectively.

To demonstrate a causal hypothesis, the existence of a cause-effect relationship or a statistical relationship must be determined. It can also be demonstrated by eliminating alternative explanations. The formulation of these hypotheses is of the type: «If … then …».

Example

“If a student studies 10 extra hours a week, then his grades improve by one point in ten.”

#### 4- Alternative hypotheses

Alternative hypotheses try to answer the same problem as working hypotheses. However, as the name implies, they look for different possible explanations. Therefore, it is possible to test different hypotheses in the course of the same investigation.

Formally, these hypotheses are analogous to the working hypothesis. They can also be classified as attributive, associative and causal.

Other types of hypothesis

Some authors identify other types of less common hypotheses. For example:

- – Relative hypotheses

The relative hypotheses evaluate the influence of two or more variables in another.

Example

“The effect of the increase in prices on the number of university students is less than the effect of the fall in salaries on the number of university students.”

- Variable 1: price increase
- Variable 2: fall in wages

Dependent variable: number of university students.

- – Conditional hypotheses

Conditional hypotheses assume that one variable depends on the value of two others. In this case, the hypotheses are similar to the causal ones, but there are two variables “cause” and a variable “effect”.

Example

“If the student does not bring the exercise and arrives late, he / she will be expelled from the class”.

- Cause 1: do not bring the exercise.
- Cause 2: arrive late
- Effect: being expelled.

For the “effect” variable to be fulfilled, it is not enough that one of the two “cause” variables be met: both must be fulfilled.

Possible alternative classifications

The classification of the hypothesis of the scientific research that has been exposed is the most usual. However, it is also possible to classify the hypotheses based on other criteria.

For example, it is possible to distinguish between probabilistic and deterministic hypotheses.

- – Probabilistic hypotheses

These hypotheses suggest that there is a relationship between the variables that is fulfilled in the majority of the population.

Example

«If a student does not study, he will suspend».

- – Deterministic hypotheses

These hypotheses propose relationships between the variables that are always met.

Example

“If a student does not show up for the exam, they will suspend it.”