About Standard Deviation, Variance & Z-Score Calculator
Comprehensive statistical analysis engine for students, researchers, data scientists, and engineers. Computes sample standard deviation (s with Bessel's n - 1 correction) and population standard deviation (σ with N), sample/population variance, standard error of the mean (SEM), sum of squared deviations (SS), mean, median, range, and normal distribution Z-scores with step-by-step calculation tables. 100% private.
Key Capabilities & Features
- Sample (n - 1) and Population (N) mode toggle
- Automatic dataset parsing supporting commas, spaces, and line breaks
- Standard error of the mean (SEM) and sum of squared deviations (SS)
- Interactive Z-score evaluator with normal distribution percentile probability
- Full step-by-step deviation table showing (x - x̄) and (x - x̄)²
- One-click copy of statistical summary
How to Use Standard Deviation, Variance & Z-Score Calculator
Enter Dataset
Paste or type numbers separated by commas, spaces, or newlines.
Select Data Mode
Choose Sample (n - 1) for a representative sample or Population (N) for an entire dataset.
Inspect Deviations
View the step-by-step calculation table showing individual squared deviations.
Evaluate Z-Scores
Test any individual value to calculate its Z-score and normal curve percentile.
Privacy & In-Browser Execution Guarantee
100% private. All statistical analysis and datasets are evaluated locally in browser RAM.
Frequently Asked Questions
When should I use Sample vs Population standard deviation?
Use Sample (n - 1) when your dataset is a sample representing a larger group. Use Population (N) when your dataset contains every member of the entire population.
What is the Standard Error of the Mean (SEM)?
SEM measures how much the sample mean of the data is likely to deviate from the true population mean, calculated as s / √n.