Statistics Foundation · Lesson 2.1
Measures of centre.
Measures of centre describe where data tend to gather. In this lesson, students learn how the mean, median and mode represent different ideas of a typical value, why the mean is sensitive to outliers, why the median is safer for skewed data, and how to choose a centre that matches the variable and the shape of the distribution.
90–100 minute lesson plan
Learn how to describe a typical value carefully.
Descriptive statistics begins with summarising data. A measure of centre gives one number or category that represents where the data are located. But the word “typical” has more than one meaning. The mean, median and mode answer different questions.
0–10 min
What does a typical value mean?
Begin by understanding that a measure of centre is not just a calculation. It is a summary of where the data tend to gather.
10–30 min
Mean, median and mode
Learn the three main measures of centre, how they are calculated, and what each one is trying to represent.
30–45 min
When the mean works well
Study why the mean is powerful for balanced numerical data, but sensitive to extreme values.
45–60 min
When the median is safer
Understand why the median is resistant to outliers and often better for skewed data such as income, waiting time or house prices.
60–80 min
Interactive centre lab
Adjust skewness, outliers and repeated values to see how the mean, median and mode respond differently.
80–100 min
Worked examples and quiz
Practise choosing the most appropriate measure of centre for real educational, medical and everyday datasets.
Mastery checklist
By the end, centre should feel like interpretation, not just arithmetic.
Explain what a measure of centre is trying to summarise.
Calculate and interpret the mean, median and mode.
Explain why the mean is sensitive to outliers.
Explain why the median is useful for skewed data.
Identify when the mode is the correct summary.
Choose the most appropriate centre for a real dataset.
Write a careful sentence interpreting the chosen centre.