This site is intended for healthcare professionals

Go to /sign-in page

You can view 5 more pages before signing in

Null hypothesis

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

  • a null hypothesis is a formal statement that no difference exists between treatment groups (e.g. placebo versus treatment to be tested) or that there is no association between risk indicator and outcome variables. A null hypothesis is stating that any difference between the different treatment groups, or risk indicator and outcome variables, is due to chance alone.
  • it is a hypothesis which is set up to be disproved by the results of a trial
  • if the null hypothesis is true then the findings from the study are the result of chance or random factors. If a null hypothesis is rejected then, depending on the factors tested by the trial, there is evidence of a difference between treatment groups or an anssociation between risk indicator and outcome variables
  • the predicted results given the accuracy of the null hypothesis are used to assess the statistical validity of the results of the trial

Relating the null hypothesis to type 1 error, type 2 error and the power of a study:

  • null hypothesis - assumes that there is no difference between the groups (treatment versus placebo)
  • type 1 error - alpha - the probability of rejecting a null hypothesis that should have been accepted, i.e. the probability of accepting an alternative hypothesis when an observation is due to chance
  • type 2 error - beta - the probability that, despite accepting the null hypothesis (i.e. no evidence from the study results that there is a a difference between placebo and treatment), there really is a difference
  • the power of a study is calculated as (1 - type 2 error)

Create an account to add page annotations

Add information to this page that would be handy to have on hand during a consultation, such as a web address or phone number. This information will always be displayed when you visit this page

The content herein is provided for informational purposes and does not replace the need to apply professional clinical judgement when diagnosing or treating any medical condition. A licensed medical practitioner should be consulted for diagnosis and treatment of any and all medical conditions.

Connect

Copyright 2024 Oxbridge Solutions Limited, a subsidiary of OmniaMed Communications Limited. All rights reserved. Any distribution or duplication of the information contained herein is strictly prohibited. Oxbridge Solutions receives funding from advertising but maintains editorial independence.