z-Score (Standard Score)

z-Score (Standard Score)

ST-02
ASPCSPFoundational

Formula
z = (x − X̄) ÷ s
When to Use

Calculate how many standard deviations a value is from the mean. Used for comparing values across different distributions.

Symbol Legend
SymbolMeaningUnitNote
zStandard scoreStandard deviations from mean
xIndividual observed valuesame as data
X̄Mean of the data setsame as data
sStandard deviation of samplesame as data

🔒

Worked Example for Blueprint Members

Blueprint members get full exam-style worked problems, step-by-step solutions, solution videos, common exam traps, and linked practice questions — for every equation.

Join Be Safe ASP | CSP Blueprint™ →