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Module · Math · Statistics
Z-Score Calculator
Compute the Z-score for a raw value against a normal distribution — plus probabilities (P(X<x), P(X>x), P within interval) using Abramowitz-Stegun normal CDF.
1.2000
Z = (X − μ) / σ
P(X < x) — cumulative88.4930%
P(X > x)11.5070%
P(within |z| of mean)76.9861%
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Guide
How Z-Score Calculator works
Step 01
Enter X, μ, σ
Raw value, mean and standard deviation of your distribution.
Step 02
See Z
Z = (X − μ) / σ — the number of standard deviations from the mean.
Step 03
Get probabilities
Cumulative below, above and interval coverage from the normal CDF.
FAQ
Frequently asked
What does a Z-score of 2 mean?+
The value is 2 standard deviations above the mean. About 97.7% of a normal distribution lies below Z = 2.
Which formula is used for the normal CDF?+
The Abramowitz-Stegun approximation (accurate to ~7 decimal places).