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Hypothesis Negative Correlation Positive Correlation Research Design Research Topics Alternative Hypothesis Null Hypothesis Hypothesis Types Experiment Design Random Assignment # 9 Types of Hypothesis

, February 25, 2021 A hypothesis is a prediction that is used as the starting point of research such as an experiment. This has several important types:

## Null Hypothesis

A hypothesis predicts the relationship between independent and dependent variables. An independent variable is something you change as part of an experiment such as the amount of water given to a plant. A dependent variable is something that is predicted to change as a result such as the growth rate of a plant. The null hypothesis is the prediction that there will be no such change such that there is no relationship between the independent and dependent variables. This is an important hypothesis that is often listed in an experiment design.
Question
Does citronella oil repel mosquitoes?

Null Hypothesis
Citronella oil dispersed into the air will have no influence on the number of mosquitoes bites suffered by people at an outdoor meal.

## Research Hypothesis

Research is meant to be a valuable exploration that builds on existing knowledge. As such, a hypothesis is meant to be a brave prediction of what may happen in an experiment. This can be the null hypothesis or it can be a predication of a relationship between the independent and dependent variables.
Question
Do superhero movies influence self-confidence?

Research Hypothesis
People will report higher self-confidence directly after watching highly rated superhero movies.
In the example above, the independent variable is watching a movie and the dependent variable is self-reported self-confidence.

## Alternative Hypothesis

An alternative hypothesis is a hypothesis that there is a relationship between the independent and dependent variables. This term is used to contrast with the null hypothesis that predicts no such relationship. The research hypothesis can be either the null hypothesis or an alternative hypothesis.
Question
Does crystal glassware leach less lead over time?

Alternative Hypothesis
The amount of lead leached by crystal glassware will have a negative correlation with the number of times the glassware is used.

## Associative Hypothesis

An associative hypothesis is a prediction that two variables will be correlated without making any assertion of a cause and effect relationship.
Question
How does total average hours of sunlight in a city influence vitamin D levels in city residents?

Associative Hypothesis
There is a positive correlation between average hours of sunlight and vitamin D levels.
A positive correlation indicates that an increase in the independent variable will lead to an increase in the dependent variable and vice versa.

## Non-directional Hypothesis

A non-directional hypothesis is a weak hypothesis that simply states the independent and dependent variable are correlated without stating the direction of this correlation, i.e. whether the correlation is positive or negative.
Question
Is excessive alcohol consumption a predictor of creditworthiness?

Non-directional Hypothesis
Binge drinking behaviors will have a correlation with low credit scores.

## Directional Hypothesis

A directional hypothesis is a hypothesis that states the direction of correlation without necessarily implying causation.
Question
Is excessive alcohol consumption a predictor of creditworthiness?

Associative Hypothesis
Binge drinking behaviors will have a negative correlation with credit scores.
A negative correlation indicates that an increase in the independent variable leads to a decrease in the dependent variable.

## Causal Hypothesis

A causal hypothesis predicts that change to an independent variable causes change to the dependent variable.
Question
Does sleep deprivation decrease academic performance?

Causal Hypothesis
Cramming all night before an exam with no sleep will result in lower examination scores.
The hypothesis above predicts that a specific behavior, not sleeping, will cause a specific result, lower grades.

## Statistical Hypothesis

A statistical hypothesis is simply a prediction that involves many observations such that it requires statistical analysis to evaluate.
Question
Can regular organic coffee drinkers taste the difference between organic and non-organic coffee?

Statistical Hypothesis
Organic coffee drinkers will not be able to taste the difference between organic and non-organic coffee such that their choices will resemble random guesses.

## Complex Hypothesis

School textbooks sometimes claim that a hypothesis must have exactly one independent variable and one dependent variable. This isn't always the case. A complex hypothesis is a hypothesis with multiple independent variables and/or multiple dependent variables.
Question
How does poverty influence quality of life?

Complex Hypothesis
Poverty is negatively correlated with educational outcomes, health, life expectancy and stress levels.
 Overview: Hypothesis Types Type Definition A prediction that is used as the starting point of research such as an experiment. Related Concepts

## Experiments

This is the complete list of articles we have written about experiments.
Alternative Hypothesis
Causality
Cohort
Control Group
Controls
Dependent Variable
Empirical Evidence
Empiricism
Experiment Design
Experimental Error
Experiments
Explanatory Power
Falsifiability
Hypothesis
Measurement
Natural Experiment
Negative Control
Negative Correlation
Null Hypothesis
Original Research
Positive Control
Positive Correlation
Precision
Primary Research
Qualitative Info
Random Assignment
Random Error
Scientific Control
Scientific Fact
Soft Science
Statistics
Systematic Error

## Hypothesis

The definition of hypothesis with examples.

## Positive Correlation

The definition of positive correlation with examples and comparisons.

## Negative Correlation

The definition of negative correlation with examples.

## Null Hypothesis

The definition of null hypothesis with examples.

## Alternative Hypothesis

The definition of alternative hypothesis with examples.

## Science Vocabulary

An a-z list of important words in science with straightforward definitions.

## Science Words

An a-z list of foundational science vocabulary.

## Research Design

An overview of the common types of research design.

## Experiments

A guide to designing and conducting experiments.

## Physics

A list of the branches of physics.

## Hard Science

A list of the hard sciences.

## Soft Science

The definition of soft science with a list of its basic characteristics.

## Words To Describe Science

A vocabulary for describing science, research and scientific knowledge.

## Experiment Design

Full examples of an experiment design using a useful template.
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## New Articles

Recent posts or updates on Simplicable.
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