## Research Hypothesis: Definition, Types, & Examples

Saul Mcleod, PhD

Educator, Researcher

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul Mcleod, Ph.D., is a qualified psychology teacher with over 18 years experience of working in further and higher education.

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Olivia Guy-Evans

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BSc (Hons), Psychology, MSc, Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

A hypothesis (plural hypotheses) is a precise, testable statement of what the researcher(s) predict will be the outcome of the study. It is stated at the start of the study.

This usually involves proposing a possible relationship between two variables: the independent variable (what the researcher changes) and the dependent variable (what the research measures).

In research, there is a convention that the hypothesis is written in two forms, the null hypothesis, and the alternative hypothesis (called the experimental hypothesis when the method of investigation is an experiment ).

A fundamental requirement of a hypothesis is that is can be tested against reality, and can then be supported or rejected.

To test a hypothesis the researcher first assumes that there is no difference between populations from which they are taken. This is known as the null hypothesis. The research hypothesis is often called the alternative hypothesis.

In This Article

## Types of research hypotheses

## Null Hypothesis

## Nondirectional Hypothesis

E.g., there will be a difference in how many numbers are correctly recalled by children and adults.

## Directional Hypothesis

E.g., adults will correctly recall more words than children.

## Falsifiability

## Can a hypothesis be proven?

Upon analysis of the results, an alternative hypothesis can be rejected or supported, but it can never be proven to be correct. We must avoid any reference to results proving a theory as this implies 100% certainty, and there is always a chance that evidence may exist which could refute a theory.

## How to write a hypothesis

- 1. To write the alternative and null hypotheses for an investigation, you need to identify the key variables in the study.The independent variable is manipulated by the researcher and the dependent variable is the outcome which is measured.
- 2. Operationalized the variables being investigated.Operationalisation of a hypothesis refers to the process of making the variables physically measurable or testable, e.g. if you are about to study aggression you might count the number of punches given by participants
- 3. Decide on a direction for your prediction. If there is evidence in the literature to support a specific effect on the independent variable on the dependent variable, write a directional (one-tailed) hypothesis.If there are limited or ambiguous findings in the literature regarding the effect of the independent variable on the dependent variable, write a non-directional (two-tailed) hypothesis.
- 4. Write your hypothesis. A good hypothesis is short (i.e. concise) and comprises clear and simple language.

## What are examples of a hypothesis?

- The alternative hypothesis states that students will recall significantly more information on a Monday morning than on a Friday afternoon.
- The null hypothesis states that there will be no significant difference in the amount recalled on a Monday morning compared to a Friday afternoon. Any difference will be due to chance or confounding factors.

## What is the difference between a one-tailed hypothesis and a two-tailed hypothesis?

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## Two-tailed or one-tailed test?

Travis Dixon April 13, 2021 Internal Assessment (IB)

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## The Easy Answer

- If you have a one-tailed hypothesis, you must do a one-tailed inferential test.
- If you have a two-tailed hypothesis, you must do a two-tailed test.

The one vs two tailed debate still continues in Psychology ( read more ). The IB ignores this and makes it simple: one tailed hypotheses = one tailed test. No ifs, ands, or buts!

- Blog: Hypotheses – How to write hypotheses
- Blog: Lesson Idea: Inferential Statistics
- Video: How to do the Mann Whitney U test online
- Video: Internal Assessment Playlist

## One vs two-tailed hypothesis: What’s the difference?

## The best online calculator?

Travis Dixon is an IB Psychology teacher, author, workshop leader, examiner and IA moderator.

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or with a directional correlational hypothesis….

With a non-directional or two tailed hypothesis…

there will be NO correlation between variable A and variable B.

## Exam Techniques/Advice

- Remember, a decent hypothesis will contain two variables, in the case of an experimental hypothesis there will be an IV and a DV; in a correlational hypothesis there will be two co-variables
- both variables need to be fully operationalised to score the marks, that is you need to be very clear and specific about what you mean by your IV and your DV; if someone wanted to repeat your study, they should be able to look at your hypothesis and know exactly what to change between the two groups/conditions and exactly what to measure (including any units/explanation of rating scales etc, e.g. “where 1 is low and 7 is high”)
- double check the question, did it ask for a directional or non-directional hypothesis?
- if you were asked for a null hypothesis, make sure you always include the phrase “and any difference/correlation (is your study experimental or correlational?) that does arise will be due to chance alone”

## Practice Questions:

A There will be a difference in the levels of attendance between the two psychology groups.

B Students’ level of attendance will be higher in Mr Faraz’s group than Mr Simon’s group.

C Any difference in the levels of attendance between the two psychology groups is due to chance.

D The level of attendance of the students will depend upon who is teaching the groups.

Write a fully operationalised non-directional (two-tailed) hypothesis for Tracy’s study. (2)

4. Which of the following is a non-directional (two tailed) hypothesis?

A There is a difference in driving ability with men being better drivers than women

B Women are better at concentrating on more than one thing at a time than men

C Women spend more time doing the cooking and cleaning than men

D There is a difference in the number of men and women who participate in sports

## Revision Activity

writing-hypotheses-revision-sheet

Quizizz link for teachers: https://quizizz.com/admin/quiz/5bf03f51add785001bc5a09e

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## IMAGES

## VIDEO

## COMMENTS

A non-directional (two-tailed) hypothesis predicts that the independent variable will have an effect on the dependent variable

Both one-tailed and two-tailed hypothesis are examples of alternative or experimental hypothesis, which predict there will be a psychological effect.

A one-tailed test, also known as a directional hypothesis, is a test of significance to determine if there is a relationship between the

A 1-tailed hypothesis involves "sticking your neck out" since you're more likely to be wrong if you try to predict the direction the results will take. When you

When you perform a two-tailed test, you split the significance level percentage between both tails of the distribution. In the example below, I use an alpha of

One vs two-tailed hypothesis: What's the difference? ... If you are predicting that one of your conditions in your experiment will have a higher

In statistics you compare a sample (Example: one class of high school seniors SAT scores) and compare it to a larger set of numbers which is called a

Hypothesis, Alternative & Null Directional Non-Directional One-tailed Two-tailed @aicepsychology6667. 8.9K views 3 years ago.

How to calculate One Tail and Two Tail Tests For Hypothesis Testing. · How to Decide Whether to Reject or Fail to Reject a Null Hypothesis.

Directional hypothesis: A directional (or one tailed hypothesis) states which way you think the results are going to go, for example in an experimental