Key Idea: Standard Deviation

Standard deviation measures how spread out the numbers in a data set are from the mean (average).

General Rule:

• A small standard deviation → numbers are close to the mean.

• A large standard deviation → numbers are more spread out.

• Standard deviation is calculated using the square root of the average squared differences from the mean.

Why this matters for the SAT:

Standard deviation helps describe data variability in statistics problems.
Understanding it allows you to compare data sets and interpret how consistent or dispersed the values are.