Normal Distributions (AQA GCSE Psychology): Revision Note

Exam code: 8182

Claire Neeson

Written by: Claire Neeson

Reviewed by: Lucy Vinson

Updated on

The characteristics of a normal distribution

  • Distribution in psychology refers to the spread of data around the mean for a specific sample or population

  • Researchers in psychology are interested in seeing the extent to which one data set varies from the mean i.e. do most scores cluster around the mean, are they spread symmetrically or are they skewed?

  • A normal distribution is symmetrical around the mean, with most scores being close to it, showing a peak in the middle where the mean value is located

  • The shape of a normal distribution is known as the ‘bell curve’ as when a line is drawn around the histogram bars as in the below example, it looks like a bell

normal-distribution-curve-sq

Normal distribution of data

Interpreting normal distribution

  • In a perfect normal distribution the mean, mode and median all appear at the peak of the curve i.e. they have similar values

  • Scores to the left of the peak represent people who have scored less than the mean

  • Scores to the right of the peak represent people who have scored more than the mean

  • Each ‘tail’ (the far left and right ends of the curve) never touch the x-axis as there is no assumption made as to what the most extreme score could be (i.e. there could be people in that population who have not been measured for that particular data set who may have lower or higher scores)

  • Normal distributions are most likely for the following measurements:

    • Height

    • Shoe size

    • IQ

Worked Example

Here is an example of a question you might be asked on this topic for AO1.

AO1: You need to demonstrate knowledge and understanding of key concepts, ideas, theories and research.

Question: Which of the following sets of data is normally distributed? 

Select one answer only. [1 ]

   a) mean = 45 median = 44 mode = 43

   b) mean = 48 median = 40  mode = 46 

   c) mean = 47 median = 47 mode = 47 

   d) mean = 49 median = 46 mode = 44

Model answer:

  • The correct answer is c) mean = 47 median = 47 mode = 47 

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Claire Neeson

Author: Claire Neeson

Expertise: Psychology Content Creator

Claire has been teaching for 34 years, in the UK and overseas. She has taught GCSE, A-level and IB Psychology which has been a lot of fun and extremely exhausting! Claire is now a freelance Psychology teacher and content creator, producing textbooks, revision notes and (hopefully) exciting and interactive teaching materials for use in the classroom and for exam prep. Her passion (apart from Psychology of course) is roller skating and when she is not working (or watching 'Coronation Street') she can be found busting some impressive moves on her local roller rink.

Lucy Vinson

Reviewer: Lucy Vinson

Expertise: Psychology Content Creator

Lucy has been a part of Save My Exams since 2024 and is responsible for all things Psychology & Social Science in her role as Subject Lead. Prior to this, Lucy taught for 5 years, including Computing (KS3), Geography (KS3 & GCSE) and Psychology A Level as a Subject Lead for 4 years. She loves teaching research methods and psychopathology. Outside of the classroom, she has provided pastoral support for hundreds of boarding students over a four year period as a boarding house tutor.