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Statistics for Psychologists – Data and the T-test

4. Null Hypothesis Significance Testing

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In this lecture, we think about null hypothesis significance testing (NHST), focusing in particular on: (i) inferential statistics and how they can provide estimates for the representativeness of a sample compared to a population, and whether there is a significant difference between two or more datasets; (ii) the underpinnings of the null hypothesis, highlighting that it is only ever possible reject or fail to reject a hypothesis, rather than prove one to be correct; (iii) the four principles of NHST: scientific questions are posed in pairs of hypotheses (null and alternative), inferential statistics are used to assess whether a hypothesis is or is not true, the p-value (probability of that truth) is compared to a threshold level, and that a hypothesis is never accepted, only rejected; (iv) an analogy contextualising the idea of proof in a courtroom example on verdict of guilt.


In this course, Dr Andrew Bell (Kings College London) introduces statistics for psychologists and the t-test. In the first lecture, we are introduced to the different types of data which might be analysed for a scientific study. In the second lecture, we think about descriptive statistics, specifically mean, variance, and standard deviation. In the third lecture, we explore data distributions, working through normal (or Gaussian), leftward skewed, and rightward skewed graphs. Next, we think about null hypothesis significance testing (NHST), highlighting the importance of understanding what is meant by rejecting and not rejecting a hypothesis. In the fifth lecture, we think about the t-test, outlining the similarities and differences between a one sample, independent samples, and paired samples test. In the sixth and final lecture, we work through an example of each of the three t-tests to solidify our understanding.


Dr Andrew Bell is a lecturer in cognitive neuroscience in the Institute of Psychiatry, Psychology and Neuroscience at King’s College London. Dr Bell works in the neuroimaging department and focuses his teaching on statistics and statistical techniques. Dr Bell is a senior fellow of the Higher Education Academy and has published a review of animal lesion techniques used by researchers of human neuropsychology. Dr Bell’s recent publications include ‘Preserved extrastriate visual network in a monkey with substantial, naturally occurring damage to primary visual cortex’ (2019) and ‘Viewing ambiguous social interactions increases functional connectivity between frontal and temporal nodes of the social brain’ (2021).

Cite this Lecture

APA style

Bell, A. (2022, February 10). Statistics for Psychologists – Data and the T-test - Null Hypothesis Significance Testing [Video]. MASSOLIT.

MLA style

Bell, A. "Statistics for Psychologists – Data and the T-test – Null Hypothesis Significance Testing." MASSOLIT, uploaded by MASSOLIT, 15 Feb 2022,

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