Null Hypothesis

The practice of science involves formulating and testing hypotheses, statements that are capable of being proven false using a test of observed data. The null hypothesis typically corresponds to a general or default position. For example, the null hypothesis might be that there is no relationship between two measured phenomena or that a potential treatment has no effect.

The term was originally coined by English geneticist and statistician Ronald Fisher in 1935. It is typically paired with a second hypothesis, the alternative hypothesis, which asserts a particular relationship between the phenomena. Jerzy Neyman and Egon Pearson formalized the notion of the alternative. The alternative need not be the logical negation of the null hypothesis; it predicts the results from the experiment if the alternative hypothesis is true. The use of alternative hypotheses was not part of Fisher's formulation, but became standard.

The null hypothesis can never be proven. Data, such as the results of an observation or experiment, can only reject or fail to reject a null hypothesis. For example, if comparison of two groups (for example, comparing subjects treated with a medication with untreated subjects) reveals no statistically significant difference between the two, it does not prove that there really is no difference; it only shows that the results were not sufficient to reject the null hypothesis.

Read more about Null Hypothesis:  Principle, Testing For Differences, Terminology, Directionality, Sample Size

Other articles related to "null hypothesis, hypothesis, null":

results">Constellation Model - The Method of Weber and Welling Et Al. - Classification
... by considering the ratio where denotes the null hypothesis, which explains all parts as background noise ... In the numerator, the sum includes all hypotheses, including the null hypothesis, whereas in the denominator, the only hypothesis consistent with the absence of an object is the null ...
Marketing Research Mix - Purpose
... Many marketers avoid the term hypothesis entirely and tend to use the words “research objective” or “aim” ... The word hypothesis (plural, hypotheses) is quite different from the terms mentioned above ... Some people argue that we should only test one hypothesis others say we should test several ...
Hypotheses, Concepts and Measurement - Statistical Hypothesis Testing
... that is, at least to some extent and for some patients, the hypothesis that a relation exists cannot be examined the same way one might examine a proposed new law of ... In statistical hypothesis testing two hypotheses are compared, which are called the null hypothesis and the alternative hypothesis ... The null hypothesis is the hypothesis that states that there is no relation between the phenomena whose relation is under investigation, or at least not of the form given by the alternative hypothesis ...
Null Hypothesis - Sample Size
... Statistical hypothesis testing involves performing the same experiment on multiple subjects ... Even if a null hypothesis does not hold for the population, an insufficient sample size may prevent its rejection ... The significance level is the probability of rejecting the null hypothesis when the null hypothesis holds in the population ...
... the effect size that is just as well supported by the data as the null hypothesis ... The null hypothesis is a hypothesis set up to be tested against an alternative ... Thus the counternull is an alternative hypothesis that, when used to replace the null hypothesis, generates the same p-value as had the original ...

Famous quotes containing the words hypothesis and/or null:

    The great tragedy of science—the slaying of a beautiful hypothesis by an ugly fact.
    Thomas Henry Huxley (1825–95)

    A strong person makes the law and custom null before his own will.
    Ralph Waldo Emerson (1803–1882)