midStatistics
What is a z-score and how is it used?
Updated May 17, 2026
Short answer
Z-score measures how many standard deviations a value is from the mean.
Deep explanation
It standardizes data using (x - mean) / std, enabling comparison across distributions.
Real-world example
Standardized test scores comparison.
Common mistakes
- Ignoring assumption of normality in interpretation.
Follow-up questions
- What does z = 0 mean?
- What is z-score used for?