lesson
Read the scale before calculating
1 · Learn
The mean is the total of numerical values divided by their number. It need not equal an observed value. An unusual large value can affect it, so explain what the data represents.
A line graph can display changes over time. Read axis labels, units and intervals before interpreting a rise or fall. Joining points does not prove exactly what happened between measurements.
2 · Worked example
Recorded lengths are 6, 8, 9 and 13 cm. Their total is 36 cm and the mean is 9 cm. For readings at separate times, I distinguish measured points from estimates between them.
3 · Your turn
Find the mean of 7, 8, 10 and 15. Does that mean every observation was 10?
Check your answer
The mean is 10. No: none of the other values changes to 10; the mean summarises the set.
4 · Apply your learning
Plot an invented time series with equal time intervals and explain a trend and one limitation.
Adult guidance and safety
Ask the learner to explain the method and check it using a different representation. Supply place-value grids, fraction strips, accurate diagrams and measuring tools where needed. These examples need varied practice; a short correct answer alone does not establish fluency.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
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