Free Z-score calculator. Calculate standard score from data point, mean, and standard deviation. Shows percentile rank.
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Z-Score Calculator
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Formula
Formula
Z = (x − μ) ÷ σ
x = data point · μ = population mean · σ = standard deviation. Z=0 is at mean. Z=1 is one SD above mean (84th percentile). Z=-1 is one SD below (16th percentile).
Frequently Asked Questions
What is a Z-score?+
A Z-score shows how many standard deviations a value is from the mean. Z=0 means exactly average. Z=2 means 2 SDs above average (top ~2.3%).
What Z-score is considered significant?+
In hypothesis testing, |Z| > 1.96 is significant at 95% confidence. |Z| > 2.576 at 99% confidence.