7th Grade · Statistics & Probability
Variability
7.SP.A.2
Definition
A measure of how much data values differ from each other. High variability means data is spread out; low variability means data is clustered. Measured by range, MAD, or IQR.
Examples
- Set A {5,6,6,7,7,7,8,8,9}: range 4, MAD ≈ 0.9 — low variability, tightly clustered.
- Set B {0,0,0,0,7,10,14,14,18}: same mean 7, but range 18, MAD ≈ 6.2 — high variability.
Key rule
Same mean can hide very different spreads — always check variability too.
Memory hook
How spread out, not just where the center is.