Calculate the Z-Score to understand how a value compares to a population mean in terms of standard deviations.
Z-Score:
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About Z-Score

The Z-Score measures how many standard deviations a value is from the population mean. Positive scores indicate values above the mean, negative below.

How It Works

Formula: Z = (X - μ) / σ. Enter your value (X), the population mean (μ), and standard deviation (σ) to calculate the Z-Score.

Interpretation

- |Z| < 1 → within 1 SD from mean (typical)
- |Z| 1–2 → slightly unusual
- |Z| 2–3 → unusual
- |Z| > 3 → very unusual/extreme

Advice

Z-Scores are useful in statistics for comparing scores from different distributions, detecting outliers, or standardizing values for further analysis.

FAQs

Can Z be negative? Yes, negative Z indicates below mean.
What if SD = 0? Standard deviation cannot be zero; it must be >0.
Is this exact? It is mathematically exact for the numbers you input.