Understanding Z-Scores: A Measure for Comparing Student and School Performance, Slides of Probability and Statistics

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What is a Z-Score?

A quick review of z-scores and how

to understand them

Z-Score “Information Sheet”

• Z-scores are a standardized measure that helps

you compare individual student (or school) data

to state average data.

Student z-score =

(Student Scale Score) – (Statewide average of scale scores)

Standard Deviation of Scale Score

School z-score=

(School Value) – (Statewide average of that value)

Standard deviation of that value

Z-Score Examples

• Your school has a z-score of 1.5. You are better

than the state average.

State

Average

…Worse than state average Better than state average….

Z-score of 1.

Z-Score Examples

• Your school has a z-score of .2. You are better

than the state average, but not by a lot.

State

Average

…Worse than state average Better than state average….

Z-score of 1.

Z-score of 0.