The Logic of Null Hypothesis Significance Testing (NHST)

In this video I explain the logic of null hypothesis significance testing and how researchers use a null hypothesis and a comparison distribution or sampling distribution in order to assess the probability of a particular test statistic or calculation.
*Sample Answers to Review Questions
Why do researchers generate a null hypothesis?
Researchers generate a null hypothesis in order to compare a result to a distribution in which there is no difference between conditions, or where the manipulation or intervention has not had any effect.
What's the default assumption when thinking about the null and research hypotheses?
The default assumption is always that the null hypothesis is true. This assumption must be shown to be statistically unlikely before any other alternative hypotheses can be considered.
What is a comparison distribution or a sampling distribution?
A comparison distribution or sampling distribution is the distribution of possible values for a calculation or test statistic that is created using estimates for the population when the null hypothesis is true, or when there is no effect. This allows for the estimation of the probability of getting a particular result for that test statistic if the null hypothesis is true.
When using a NHST approach & drawing a conclusion from data, what are the two options that researchers have?
Researchers can either reject the null hypothesis or fail to reject the null hypothesis.
What does it mean if researchers fail to reject the null hypothesis?
If researchers fail to reject the null hypothesis, this means that the test statistic result is likely to have come from the comparison distribution in which the null is true. This implies that the null hypothesis is sufficient for explaining the observed result and that other explanations are not needed. This does not mean that the null hypothesis is definitely true (or that the research hypothesis is not true), but that the null being true is a likely explanation for what was observed.
What does it mean if researchers reject the null hypothesis?
If researchers reject the null hypothesis, this means that the test statistic result is unlikely to have come from the comparison distribution in which the null is true. This doesn't mean that the null isn't true (or that the research hypothesis is true), but it implies the possibility that the test statistic result might be coming from a different distribution, perhaps one where the research hypothesis (or some other alternative) might provide a more likely explanation for what was observed.

[@mundoeuniverso5123]

Great video! As a EPPP prepie I just want to thank you for sharing all these info.

[@PsychExamReview]

Thanks, glad you liked it and hope you do well!