null hypothesis

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null hypothesis

[′nəl hī′päth·ə·səs]
(statistics)
The hypothesis that there is no validity to the specific claim that two variations (treatments) of the same thing can be distinguished by a specific procedure.

null hypothesis

a working hypothesis which states that there will be no statistically significant difference between the EXPERIMENTAL GROUP and CONTROL GROUP.

When an experiment is set up, or observational data collected, this is designed to test a HYPOTHESIS, or theory which has been developed from previous work. This is the EXPERIMENTAL HYPOTHESIS, and it states what the expected difference is between the groups if the theory is correct. The converse hypothesis is also conventionally stated: this is the null hypothesis, that predictions from the theory are incorrect, and there is no difference between the groups in the VARIABLE investigated. See also INDEPENDENT VARIABLE, DEPENDENT VARIABLE.