Level 3: Averages

Statistics and data · level 3 of 8 · rough age 9-10 (a guide for parents; anyone can start anywhere)

In level 2 you counted answers, made tallies and drew bar graphs. In this level you collect your own data with a plan, and then you learn to sum up a whole list of numbers with one number: the mean, the median or the mode. You find out why each one works, and why one number is never the whole story, so you also measure how spread out the data are. The level ends with two new graphs: one for comparing two groups, and one for things that change over time.

Lesson	You will be able to
Collecting your own data	Tell primary data from secondary data, and write a data plan before you start
The mean	Find the mean by levelling towers or by adding and dividing, and explain why it need not be one of the values
The median and the mode	Find the middle value of odd and even lists, and the most common value, even when there are two or none
The range	Measure how spread out data are, and explain why two groups with the same mean can be very different
Stem-and-leaf plots	Build a stem-and-leaf plot, read the median from it, and compare two groups back to back
Double bar graphs and broken-line graphs	Compare two groups with a double bar graph, show change over time with a line graph, and know when to join the points

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