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➜ SKILLS TUTORIAL
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Sample size and reliability
Are all orange cats male?
Science Progress © Hodder Education 2014
That is a scientific question.
It can be answered by making the right kind of observations.
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Sample size
There is a large population of cats to choose from.
To answer the question we need to look at some orange cats to see if they really are all male.
There are about nine million cats in the UK. But we cannot look at them all.
Science Progress © Hodder Education 2014
➜ SKILLS TUTORIAL
Skills tutorials
Sample size
The bar chart shows that this orange cat is male.
We could look at just one cat.
The cat is a sample of the whole cat population.
Does this show that all orange cats are male?
Science Progress © Hodder Education 2014
➜ SKILLS TUTORIAL
Skills tutorials
Sample size
Does this answer the scientific question?
These are the data from a sample of two orange cats.
They are both male.
Science Progress © Hodder Education 2014
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Sample size
All five cats are orange and they are all male.
Now there are five cats.
The sample is a bigger proportion of the whole cat population.
Does that prove that all orange cats are male?
Science Progress © Hodder Education 2014
➜ SKILLS TUTORIAL
Skills tutorials
Sample size
Does that prove that all orange cats are male?
It would be a good idea to look at one more cat.
The sixth cat is male.
It would be a good idea to look at one more cat again.
Science Progress © Hodder Education 2014
➜ SKILLS TUTORIAL
Skills tutorials
Sample size
How many cats would it take to prove that all orange cats are male?
The seventh cat is female.
It takes just one observation to show that the idea that all orange cats are male is false.
Science Progress © Hodder Education 2014
➜ SKILLS TUTORIAL
Skills tutorials
Reliability
One cat is a small sample of the cat population.
It is impossible to reach conclusions about the sexes of cats and their colours from a sample of one.
Even five is a small sample. The bigger the sample, the more reliable the conclusion can be.
Science Progress © Hodder Education 2014
