What it's all about
Have a very quick look at the dots above, then look away. How many dots do you think there are? Write down your first estimate.
Now get your class to do the same. Show them the image of the dots for less than a second, get them each to write down their guess, and quickly go round the class and record them on the board.
In less than three minutes you have created a data set, which will interest your pupils because they have created it and will be desperate to know how many dots there are, writes Craig Barton.
But don't tell them yet, as you have hooked them in and there is plenty of important maths to do with this little set of data. First, we can work out the mean, median, mode and range of the guesses.
Once you have done this, why not compare the results with another class that has carried out the same experiment? Which class had the better estimators? How can we tell? Your pupils will be arguing about whether the mean or median is a better measure of average, simply because they own the guesses and data.
Finally, offer them the opportunity to stick with their original guess or change it. Record this new data set on the board and ask them to predict how the mean, median, mode and range might change. The results are fascinating.
Oh, and there are 58, by the way.
For a colourful step-by-step guide to finding the mean, try Ben Cooper's worksheet, bit.lydatahandling.
Help pupils to remember mean, mode and median with Danny Barthorpe's 3M cowboys, bit.ly3Mcowboys.