Spread and Variability
How different are the values?
Why spread matters
Two data sets can have the same mean but very different spread. Variability tells us how consistent or scattered the data are.
Common spread measures
Range example
For the data , the range is .
A key idea
A small standard deviation means the values are usually close to the mean; a large one means they are more spread out.
What is the range of 3, 5, 7, 9?
Range = largest minus smallest = .
Correct answer: 6
What does standard deviation describe in simple words?
It is a common measure of variability.
Correct answer: How spread out the values are from the mean.
If two data sets have the same mean, which one has more variability?
Greater spread means greater variability.
Correct answer: The one whose values are more spread out
Name one measure of spread.
All of these describe how spread out data are.
Correct answer: Range, variance, or standard deviation.