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  • Early Years Foundation Stage

How Confident Are You?

Age 11 to 16
Challenge Level Yellow star
  • Problem
  • Teachers' Resources


guess how many smarties in the jarHow confident are you in your guesses?

Fill a container with jelly beans (or similar small items) and ask as many people as possible to guess how many there are
- but don't just ask them for a simple guess!

Ask them to specify a range which they are 90% sure contains the right answer.

So for instance if you look at the container of sweets and think there's probably somewhere around 600, you might say you think there are 9 chances out of 10 that the correct answer is between 500 and 700.

histogramRecord the results of your survey on graphs.  You could show the mid-point of each person's range on a histogram, and the ranges on a separate graph, to avoid confusion.

interval graph

Now count the number of sweets in the container. 

How many of the guessed intervals contained the right answer?
Are you surprised at what you find?
 

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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