Normal Distributions (AQA GCSE Psychology): Revision Note
Exam code: 8182
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 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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