10.3 Normal distributions
Unit 10 · Statistics and inference
Ideas in this lesson
Standardized scores
A z-score measures how many standard deviations an observation lies above or below the mean.
Empirical rule
For an approximately normal population, about 68, 95 and 99.7 percent lie within one, two and three standard deviations.
Recover a raw score
Multiply a z-score by the standard deviation and add the mean.
Compare standardized values
Compare z-scores to compare relative positions in populations with different units or spreads.
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