Z Score Calculator
Calculate the z-score (standard score) of a data point given the mean and standard deviation.
Z-Score
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Z-Score Formula
Z = (x − μ) / σ
x = 85, μ = 70, σ = 10
Z = (85 − 70) / 10 = 1.5
Z = (85 − 70) / 10 = 1.5
Interpreting Z-Scores
| Z-Score | Meaning |
|---|---|
| 0 | Equal to the mean |
| +1 | 1 standard deviation above mean |
| −1 | 1 standard deviation below mean |
| >+2 or <−2 | Unusual / potential outlier |
| >+3 or <−3 | Extremely unusual |
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Last updated: 2026-08-08