Statistical significance

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Definition: A property of a result using Null Hypothesis Significance Testing (NHST) that, given a significance level, is deemed unlikely to have occurred given the null hypothesis. Tenny and Abdelgawad (2017) defined it as “a measure of the probability of obtaining your data or more extreme data assuming the null hypothesis is true, compared to a pre-selected acceptable level of uncertainty regarding the true answer” (p. 1). Conventions for determining the threshold vary between applications and disciplines but ultimately depend on the considerations of the researcher about an appropriate error margin. The American Statistical Association’s statement (Wasserstein & Lazar, 2016) notes that “Researchers often wish to turn a p-value into a statement about the truth of a null hypothesis, or about the probability that random chance produced the observed data. The p-value is neither. It is a statement about data in relation to a specified hypothetical explanation, and is not a statement about the explanation itself” (p. 131).

Related terms: Alpha error, Frequentist statistics, Null hypothesis, Null Hypothesis Significance Testing (NHST), *P*\-value, Type I error **Incorrect definition:** Statistical significance describes the likelihood of the observed result against chance (regardless of the null hypotheses)

References:

  • Cassidy, S. A., Dimova, R., Giguère, B., Spence, J. R., & Stanley, D. J. (2019). Failing grade: 89% of introduction-to-psychology textbooks that define or explain statistical significance do so incorrectly. Advances in Methods and Practices in Psychological Science, 2(3), 233–239. https://doi.org/10.1177/2515245919858072
  • Wasserstein, R. L., & Lazar, N. A. (2016). The ASA Statement on p-Values: Context, Process, and Purpose. The American Statistician, 70, 129–133. https://doi.org/10.1080/00031305.2016.1154108

Originally drafted by: Alaa AlDoh; Flávio Azevedo

Reviewed by: James E. Bartlett, Alexander Hart**;** Annalise A. LaPlume, Charlotte R. Pennington, Graham Reid, Timo Roettger, Suzanne L. K. Stewart