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# Probability and Evidence

### Introductory Video

### Spots and Measles

### Do Rare Events Happen?

### The ELISA Test

### Matching Criminals

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An understanding of probability is important in medicine, law and wider society. These problems invite you to consider some scenarios where interpreting probabilities incorrectly can have serious consequences.

Age 11 to 16

An introductory video to the Probability and Evidence collection

Age 11 to 16

Challenge Level

99% of people who have measles have spots. Ben has spots. Do you think he has measles?

Age 11 to 16

Challenge Level

I'd be very surprised if I had three children all with the same birthday, but I read in the paper that it happened to one family...

Age 14 to 18

Challenge Level

In 1% of cases, an HIV test gives a positive result for someone who is HIV negative. How likely is it that someone who tests positive has HIV?

Age 14 to 18

Challenge Level

DNA profiling is an invaluable tool for the police. However, when it comes to probability, things aren't always as straightforward as they seem.