3.5 The normal distribution
Students should be able to recognise that many things closely follow a Normal Distribution, eg heights of people, size of things produced by machines, errors in measurements, blood pressure, marks on a test etc. In these and similar situations, a graph of the distribution will have a ‘bell’ shaped curve.
S1 Properties of the normal distribution
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S1.1 |
knowledge that this is a symmetrical distribution and that the area underneath the normal ‘bell’ shaped curve represents probability |
knowledge that approximately of observations lie within 1 standard deviation of the mean and that approximately of observations lie within 2 standard deviations of the mean |
S2 Notation
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Additional information |
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S2.1 |
use of the notation to describe a normal distribution in terms of mean and standard deviation |
use of the notation for the standardised normal distribution with mean = 0 and standard deviation = 1 |
S3 Calculating probabilities
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Additional information |
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S3.1 |
using a calculator or tables to find probabilities for normally distributed data with known mean and standard deviation |
the finding of an unknown mean or standard deviation by making use of percentage points will not be required |
