Types Of Hypotheses In Scientific Research (and Examples)
There are different types of hypotheses in scientific research. From the null, general or theoretical hypotheses, to the complementary, alternative or working hypotheses.
But, What exactly is a hypothesis and what is it for? The hypotheses specify the possible characteristics and results that may exist between certain variables that are going to be studied.
Using the scientific method, a researcher must try to verify the validity of his initial (or main) hypothesis. This is what is usually called a working hypothesis. On other occasions, the researcher has in mind several complementary, or alternative, hypotheses.
If we examine these working and alternative hypotheses we find three subtypes: attributive, causal and associative hypotheses. The general or theoretical hypotheses serve to establish a relationship (negative or positive) between the variables, while the working and alternative hypotheses are those that effectively quantify said relationship.
On the other hand, the null hypothesis is the one that reflects that there is no appreciable link between the variables studied. In the event that it cannot be verified that the working hypotheses and the alternative hypotheses are valid, the null hypothesis is accepted as correct.
Although the aforementioned are considered the most common types of hypotheses, there are also relative and conditional hypotheses. In this article we will discover all types of hypotheses, and how they are used in scientific research.
What are hypotheses used for?
Any scientific study must begin taking into account one or more hypotheses intended to confirm or refute.
A hypothesis is nothing more than a conjecture that can be confirmed, or not, through a scientific study. In other words, hypotheses are the way scientists pose the problem, establishing possible relationships between variables.
Types of hypotheses used in a scientific study
There are several criteria that can be followed when classifying the types of hypotheses used in science. We will meet them next.
1. Null hypothesis
The null hypothesis refers to the fact that there is no relationship between the variables that have been the subject of research. It is also called the “no relationship hypothesis”, but should not be confused with a negative or inverse relationship. Simply, the variables studied do not seem to follow any specific pattern.
The null hypothesis is accepted if the scientific study results in the working and alternative hypotheses not being observed.
Example
“There is no relationship between people’s sexual orientation and their purchasing power.”
2. General or theoretical hypotheses
General or theoretical hypotheses are those that scientists establish prior to the study and conceptually , without quantifying the variables. Generally, the theoretical hypothesis is born from generalization processes through certain preliminary observations about the phenomenon they wish to study.
Example
“The higher the level of education, the higher the salary.” There are several subtypes within the theoretical hypotheses. Difference hypotheses, for example, state that there is a difference between two variables, but do not measure its intensity or magnitude. Example: “In the Faculty of Psychology there are a greater number of female students than male students.”
3. Working hypothesis
The working hypothesis is the one that is used to try to demonstrate a specific relationship between variables through a scientific study. These hypotheses are verified or refuted through the scientific method, which is why they are sometimes also known as “operational hypotheses.” Generally, working hypotheses are born from deduction: based on certain general principles, the researcher assumes certain characteristics of a particular case. Working hypotheses have several subtypes: associative, attributive and causal.
The associative hypothesis specifies a relationship between two variables. In this case, if we know the value of the first variable, we can predict the value of the second.
Example
“There are twice as many students enrolled in the first year of high school as there are in the second year of high school.”
3.2. Attributive
The attributional hypothesis is the one used to describe the events that occur between the variables. It is used to explain and describe real and measurable phenomena. This type of hypothesis only contains one variable.
Example
“The majority of homeless people are between 50 and 64 years old.”
3.3. Causal
The causal hypothesis establishes a relationship between two variables. When one of the two variables increases or decreases, the other increases or decreases. Therefore, the causal hypothesis establishes a cause-effect relationship between the variables studied. To identify a causal hypothesis, a cause-effect link, or statistical (or probabilistic) relationship, must be established. It is also possible to verify this relationship through the refutation of alternative explanations. These hypotheses follow the premise: “If X, then Y.”
Example
“If a player trains 1 additional hour each day, his shooting success percentage increases by 10%.”
4. Alternative hypotheses
Alternative hypotheses attempt to provide an answer to the same question as the working hypotheses. However, and as can be deduced from its name, the alternative hypothesis explores different relationships and explanations. In this way it is possible to investigate different hypotheses during the course of the same scientific study. This type of hypothesis can also be subdivided into attributive, associative and causal.
There are other types of hypotheses that are not so common, but are also used in different types of research. They are the following.
5. Relative hypotheses
Relative hypotheses show the influence of two or more variables on another variable.
Example
“The effect of the decline in GDP per capita on the number of people who have private pension plans is lower than the effect of the fall in public spending on the rate of child malnutrition.”
6. Conditional hypotheses
Conditional hypotheses serve to indicate that one variable depends on the value of two others. This is a type of hypothesis very similar to the causal ones, but in this case there are two “cause” variables and only one “effect” variable.
Example
“If the player receives a yellow card and is also warned by the fourth referee, he must be excluded from the game for 5 minutes.”
Other types of hypotheses
The types of hypotheses that we have explained are the most commonly used in scientific and academic research. However, they can also be classified based on other parameters.
7. Probabilistic hypotheses
This type of hypothesis indicates that there is a probable relationship between two variables. That is, the relationship is fulfilled in the majority of cases studied.
Example
“If the student does not spend 10 hours a day reading, they (probably) will not pass the course.”
8. Deterministic hypotheses
Deterministic hypotheses indicate relationships between variables that are always fulfilled without exception.
Example
“If a player does not wear cleated boots, he will not be able to play the game.”
