7th Grade · Statistics & Probability
Measure of Center
7.SP.B.4
Definition
Values that represent the middle of a data set. Mean = average (sum ÷ count). Median = middle value when ordered. Choose based on whether outliers are present.
Teach it
Where it is taught, with guided notes, practice, homework, an exit ticket and an interactive Teacher Deck.
Examples
- {3,5,7,8,9,10,12}: mean ≈ 7.7, median = 8.
- House prices $150K,$160K,$170K,$1,000K: mean $370K is pulled up; median $165K is the better center.
Key rule
Use mean when data is symmetric with no outliers; use median when outliers are present.
Memory hook
Mean gets pulled by outliers; median doesn't.