**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.

## 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.

## 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.

## 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.

## 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 |