Mean and median: what changes?

Grade 6 mathematics · 15 minutes · Statistics

Calculate and compare measures of center and describe the effect of an extreme value.

Classroom activity

Five fictional reading sessions lasted 10, 12, 12, 14, and 17 minutes.

1. Find the median. Explain how you locate it.
2. Find the mean and explain what equal sharing of the total time represents.
3. Replace 17 with 42 minutes. Recalculate the mean and median.
4. Describe which measure changed and why. Which measure would you use to describe a typical session here? Justify your choice without claiming one measure is always best.

Compare explanations, including what the data do and do not tell you.

Check understanding

For 4, 5, 5, 6, and 20, find the mean and median. Explain why they differ.

Teacher guide and answers

The original median is 12 and mean is 13. Replacing 17 with 42 gives median 12 and mean 18. The extreme value affects the mean more in this example. The check mean is 8 and median 5. Support by ordering values and sharing the total with counters. Extend by constructing two data sets with the same mean but different spreads.

You may use, print, adapt, and share this example for teaching. Keep the ClassLattice attribution when redistributing the original.

Grade 6 topic reference. Confirm your adopted standards; topic guidance does not certify alignment.