What a p-value tells you about statistical significanceBy Dr. Saul McLeod, published 2019 Show
The null hypothesis states that there is no relationship between the two variables being studied (one variable does not affect the other). It states the results are due to chance and are not significant in terms of supporting the idea being investigated. Thus, the null hypothesis assumes that whatever you are trying to prove did not happen. The alternative hypothesis is the one you would believe if the null hypothesis is concluded to be untrue. The alternative hypothesis states that the independent variable did affect the dependent variable, and the results are significant in terms of supporting the theory being investigated (i.e. not due to chance). How do you know if a p-value is statistically significant?A p-value, or probability value, is a number describing how likely it is that your data would have occurred by random chance (i.e. that the null hypothesis is true). The level of statistical significance is often expressed as a p-value between 0 and 1. The smaller the p-value, the stronger the evidence that you should reject the null hypothesis.
How to report a p-value APA styleThe 6th edition of the APA style manual (American Psychological Association, 2010) states the following on the topic of reporting p-values: “When reporting p values, report exact p values (e.g., p = .031) to two or three decimal places. However, report p values less than .001 as p < .001. The tradition of reporting p values in the form p < .10, p < .05, p < .01, and so forth, was appropriate in a time when only limited tables of critical values were available.” (p. 114)Note:
Why the p-value is not enoughA lower p-value is sometimes interpreted as meaning there is a stronger relationship between two variables. However, statistical significance means that it is unlikely that the null hypothesis is true (less than 5%). To understand the strength of the difference between two groups (control vs. experimental) a researcher needs to calculate the effect size. How to reference this article:How to reference this article:McLeod, S. A. (2019, May 20). What a p-value tells you about statistical significance. Simply Psychology. www.simplypsychology.org/p-value.html How to reference this article:How to reference this article:McLeod, S. A. (2019, May 20). What a p-value tells you about statistical significance. Simply Psychology. www.simplypsychology.org/p-value.html Home | About Us | Privacy Policy | Advertise | Contact Us Simply Psychology's content is for informational and educational purposes only. Our website is not intended to be a substitute for professional medical advice, diagnosis, or treatment. © Simply Scholar Ltd - All rights reserved
When the pIf the p-value is less than or equal to the specified significance level α, the null hypothesis is rejected; otherwise, the null hypothesis is not rejected. In other words, if p≤α, reject H0; otherwise, if p>α do not reject H0.
How do you reject a hypothesis with pIf the p-value is less than 0.05, we reject the null hypothesis that there's no difference between the means and conclude that a significant difference does exist. If the p-value is larger than 0.05, we cannot conclude that a significant difference exists.
Do you reject null if pIf you conduct a statistical test using a significance level of 0.1, 0.05, or 0.01 (or any significance level greater than 0.000) and get a p-value of 0.000, then reject the null hypothesis.
Do you reject null hypothesis if pThe p-value measures the probability of getting a more extreme value than the one you got from the experiment. If the p-value is greater than alpha, you accept the null hypothesis. If it is less than alpha, you reject the null hypothesis.
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