What is a statement of predicted relationships between two or more variables in a research study?

There are seven different types of research hypotheses.

What is a statement of predicted relationships between two or more variables in a research study?

Simple Hypothesis A simple hypothesis predicts the relationship between a single dependent variable and a single independent variable. Complex Hypothesis A complex hypothesis predicts the relationship between two or more independent and dependent variables. Directional Hypothesis A directional hypothesis specifies the expected direction to be followed to determine the relationship between variables. This kind of hypothesis is derived from theory, and it also implies the researcher’s academic commitment to a particular outcome. Non-directional Hypothesis A non-directional hypothesis does not predict the exact direction or nature of the relationship between the two variables. A researcher would utilize this kind of hypothesis if it is not based on theory or when the new research findings contradict the previous research. Associative and Causal Hypothesis An associative hypothesis defines the relationship and interdependency between variables. For example, an associative hypothesis predicts that a change in one variable will result in a change of the other variable.
What is a statement of predicted relationships between two or more variables in a research study?
A causal hypothesis, on the other hand, proposes that there will be an effect on the dependent variable as a result of a manipulation of the independent variable. Null Hypothesis A null hypothesis, denoted by H0, posits a negative statement to support the researcher’s findings that there is no relationship between two variables or that any findings are the result of mere chance. Alternative Hypothesis An alternative hypothesis, denoted by H1 or Ha, challenges the null hypothesis and states that there is a relationship between the two variables of the study and that the results are significant to the research topic.

Hypothesis A statement of predicted relationship between the independent and dependent variables Example: Cigarette smoking is related to lung cancer.

Hypothesis Allows theoretical propositions to be tested Suggests an answer to the research question Provides the reader with an understanding of the researcher’s expectations Guides the research design Dictates the type of statistical analysis to be used

Testing a Hypothesis Advances scientific knowledge Supports or fails to support the tested theory

Sources or Rationale for Hypotheses Theories Personal experience Previous research studies

Generating a Hypotheses Inductive reasoning Deductive reasoning

Research Hypotheses Directional Nondirectional

Types of Hypotheses Simple Complex Research Hypothesis Null Hypothesis

Simple Hypothesis The relationship between one independent and one dependent variable Example: Birth weight is lower among infants of alcoholic mothers than among infants of nonalcoholic mothers.

Complex Hypothesis Two or more independent variables, two or more dependent variables, or both Example: More postpartum depression and feelings of inadequacy are reported by women who give birth by cesarean section than those who deliver vaginally.

Interaction Effects The action of two variables in conjunction with each other Example: Daily weight loss is greater for adults who follow a reduced calorie diet and exercise daily than for those who do not follow a reduced calorie diet and do not exercise daily.

Null Hypothesis May read as “H0” Predicts no relationship Is statistically analyzed

Research Hypothesis May read as “H1” States expected relationship between variables Can be directional or nondirectional

Directional Hypotheses States the direction of the relationship Makes a prediction between variables Comes from conceptual/theoretical frameworks or previous research

Statistical Analyses Evaluates the Null Hypothesis Significance level in nursing at or below .05

Non directional Research Hypotheses Predicts a relationship between variables Does not predict direction of relationship Example: There is a relationship between serotonin levels and SIDS.

Directional Research Hypothesis Predicts the direction of the relationship Makes researchers’ expectation clear Allows precise statistical testing Example: People who smoke are more likely to develop lung cancer than those who do not.

Nondirectional Research Hypotheses The study has no theory to base the prediction on Previous research findings may be contradictory

A Hypothesis Should (criteria) be written in a declarative sentence be written in the present tense specify the population to be studied reflect the problem statement or the purpose statement contain all the variables be empirically testable

Hypothesis Format A correlational statement A comparative statement

Hypothesis Format Promotes statistical analysis of data Uses predictive terms

Hypothesis Used to test propositions of a theory Cannot be PROVED or DISPROVED

Hypothesis If Null Hypothesis is rejected, the research hypothesis is supported. Example: Null = There is no relationship between studying and test grades.

Hypothesis Research hypothesis supported, theory also supported Research hypothesis not supported, theory also not supported Example: Research Hypothesis = Those who study get higher test grades than those who do not.

Hypotheses Needed when the relationship between variables is being studied

When aren’t Hypotheses Needed? in qualitative studies in single-variable descriptive studies in methodological studies

Research Questions May be Used in place of hypotheses in some studies in addition to hypotheses related to other areas of interest concerning the study topic

Guidelines for Critiquing Hypotheses and Research Questions Does the study contain a hypothesis or hypotheses? Is each hypothesis clearly worded and concise? Is the hypothesis written in a declarative sentence? Is each hypothesis directly tied to the study problem? If there is a clearly identified study framework, is each hypothesis derived from this framework?

Guidelines for Critiquing Hypotheses and Research Questions Does each hypothesis contain the population and at least two variables? Is each hypothesis stated as a directional research hypothesis? If not, is the rationale given for the type of hypothesis that is stated? Is it apparent that each hypothesis can be empirically tested?

Guidelines for Critiquing Hypotheses and Research Questions Does each hypothesis contain only one prediction? If the study contains research questions, are the questions precise and specific? Do the research questions further delineate the problem area of the study?

How to Write a Strong Hypothesis | Steps & Examples

A hypothesis is a statement that can be tested by scientific research. If you want to test a relationship between two or more variables, you need to write hypotheses before you start your experiment or data collection.

Example: Hypothesis

Daily apple consumption leads to fewer doctor’s visits.

Table of contents

  1. What is a hypothesis?
  2. Developing a hypothesis (with example)
  3. Hypothesis examples
  4. Frequently asked questions about writing hypotheses

What is a hypothesis?

A hypothesis states your predictions about what your research will find. It is a tentative answer to your research question that has not yet been tested. For some research projects, you might have to write several hypotheses that address different aspects of your research question.

A hypothesis is not just a guess – it should be based on existing theories and knowledge. It also has to be testable, which means you can support or refute it through scientific research methods (such as experiments, observations and statistical analysis of data).

Variables in hypotheses

Hypotheses propose a relationship between two or more variables. An independent variable is something the researcher changes or controls. A dependent variable is something the researcher observes and measures.

Example: Hypothesis
Daily exposure to the sun leads to increased levels of happiness.

In this example, the independent variable is exposure to the sun– the assumed cause. The dependent variable is the level of happiness– the assumed effect.

Developing a hypothesis (with example)

Step 1. Ask a question

Writing a hypothesis begins with a research question that you want to answer. The question should be focused, specific, and researchable within the constraints of your project.

Example: Research question
Do students who attend more lectures get better exam results?

Step 2. Do some preliminary research

Your initial answer to the question should be based on what is already known about the topic. Look for theories and previous studies to help you form educated assumptions about what your research will find.

At this stage, you might construct a conceptual framework to identify which variables you will study and what you think the relationships are between them. Sometimes, you’ll have to operationalise more complex constructs.

Step 3. Formulate your hypothesis

Now you should have some idea of what you expect to find. Write your initial answer to the question in a clear, concise sentence.

Attending more lectures leads to better exam results.

4. Refine your hypothesis

You need to make sure your hypothesis is specific and testable. There are various ways of phrasing a hypothesis, but all the terms you use should have clear definitions, and the hypothesis should contain:

  • The relevant variables
  • The specific group being studied
  • The predicted outcome of the experiment or analysis

5. Phrase your hypothesis in three ways

To identify the variables, you can write a simple prediction inif…then form. The first part of the sentence states the independent variable and the second part states the dependent variable.

If a first-year student starts attending more lectures, then their exam scores will improve.

In academic research, hypotheses are more commonly phrased in terms of correlations or effects, where you directly state the predicted relationship between variables.

The number of lectures attended by first-year students has a positive effect on their exam scores.

If you are comparing two groups, the hypothesis can state what difference you expect to find between them.

First-year students who attended most lectures will have better exam scores than those who attended few lectures.

6. Write a null hypothesis

If your research involves statistical hypothesis testing, you will also have to write a null hypothesis. The null hypothesis is the default position that there is no association between the variables. The null hypothesis is written as H0, while the alternative hypothesis is H1 or Ha.

H0: The number of lectures attended by first-year students has no effect on their final exam scores.
H1: The number of lectures attended by first-year students has a positive effect on their final exam scores.

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Hypothesis examples

Research question Hypothesis Null hypothesis
What are the health benefits of eating an apple a day? Increasing apple consumption in over-60s will result in decreasing frequency of doctor’s visits. Increasing apple consumption in over-60s will have no effect on frequency of doctor’s visits.
Which airlines have the most delays? Low-cost airlines are more likely to have delays than premium airlines. Low-cost and premium airlines are equally likely to have delays.
Can flexible work arrangements improve job satisfaction? Employees who have flexible working hours will report greater job satisfaction than employees who work fixed hours. There is no relationship between working hour flexibility and job satisfaction.
How effective is high school sex education at reducing teen pregnancies? Teenagers who received sex education lessons throughout high school will have lower rates of unplanned pregnancy than teenagers who did not receive any sex education. High school sex education has no effect on teen pregnancy rates.
What effect does daily use of social media have on the attention span of under-16s? There is a negative correlation between time spent on social media and attention span in under-16s. There is no relationship between social media use and attention span in under-16s.

Frequently asked questions about writing hypotheses

What is a hypothesis?

A hypothesis states your predictions about what your research will find. It is a tentative answer to your research question that has not yet been tested. For some research projects, you might have to write several hypotheses that address different aspects of your research question.

A hypothesis is not just a guess — it should be based on existing theories and knowledge. It also has to be testable, which means you can support or refute it through scientific research methods (such as experiments, observations and statistical analysis of data).

What are null and alternative hypotheses?

Null and alternative hypotheses are used in statistical hypothesis testing. The null hypothesis of a test always predicts no effect or no relationship between variables, while the alternative hypothesis states your research prediction of an effect or relationship.

What is hypothesis testing?

Hypothesis testing is a formal procedure for investigating our ideas about the world using statistics. It is used by scientists to test specific predictions, called hypotheses, by calculating how likely it is that a pattern or relationship between variables could have arisen by chance.

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Shona McCombes

Shona has a bachelor's and two master's degrees, so she's an expert at writing a great thesis. She has also worked as an editor and teacher, working with students at all different levels to improve their academic writing.