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Statistics
Normal Distribution Probability Calculator
Calculate the probability that a normally distributed random variable falls within a specified range, below a threshold, or above one — using the mean and standard deviation that fully describe the bell curve. Used for Six Sigma quality control, finance (VaR), psychometrics, and any process modelled by the normal distribution.
Fill in the required fields to see your result.
Statistics
Standard Deviation Calculator
Compute the sample standard deviation directly from three summary statistics — sample size n, the sum of values Σx, and the sum of squared values Σx². This is the spread metric used in virtually every empirical study, quality-control chart, and risk model.
Fill in the required fields to see your result.
Key differences
| Normal Distribution Probability Calculator | Standard Deviation Calculator | |
|---|---|---|
| Category | Statistics | Statistics |
| Inputs required | 4 | 3 |
| Result | Probability | Standard Deviation |
| What it does | Calculate the probability that a normally distributed random variable falls within a specified range, below a threshold, or above one — using the mean and standard deviation that fully describe the bell curve. Used for Six Sigma quality control, finance (VaR), psychometrics, and any process modelled by the normal distribution. | Compute the sample standard deviation directly from three summary statistics — sample size n, the sum of values Σx, and the sum of squared values Σx². This is the spread metric used in virtually every empirical study, quality-control chart, and risk model. |