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# Spots and Measles

**99% of people who have measles have spots. If Ben has red spots, how likely do you think it is it that he has measles?**

Here are three pieces of information that might help you to work out this probability:

**How might you be able to use this information to be able to calculate the probability that Ben has measles?**

Are there any tables or diagrams that might help you represent this information?

**Click below to see a possible method for organising the information:**

You could draw a two-way (or contingency) table like this.

**Can you now work out the probability that Ben has measles?**

Are there any other factors that might affect the probability that Ben has measles?

How could you factor these into the calculations?

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*This resource is part of the collection Probability and Evidence.*

Here are three pieces of information that might help you to work out this probability:

- There are about 12 million children in the UK.
- About 1,200 of these get measles every year.
- Roughly 10% of the 12 million children suffer from spots.

Are there any tables or diagrams that might help you represent this information?

You could draw a two-way (or contingency) table like this.

Measles | Not Measles | Total | |
---|---|---|---|

Spots | |||

No Spots | |||

Total | 12 000 000 |

**Can you use the information to complete the table?**

Are there any other factors that might affect the probability that Ben has measles?

How could you factor these into the calculations?