Compare calculators
Both calculators run independently — change the inputs on either side to compare results.
P-Value Calculator
Convert a z-score (or any standard-normal test statistic) into a p-value for a one- or two-tailed hypothesis test, then see it visualised as the shaded tail area on the standard normal curve. The smaller the p-value, the stronger the evidence against the null hypothesis — reject H₀ when p drops below your significance threshold (commonly 0.05).
Red shaded area is the rejection region — the probability mass in the tail(s) at least as extreme as your test statistic. A significant result means this red area is smaller than your significance level α.
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.
Key differences
| P-Value Calculator | Normal Distribution Probability Calculator | |
|---|---|---|
| Category | Statistics | Statistics |
| Inputs required | 2 | 4 |
| Result | p-value | Probability |
| What it does | Convert a z-score (or any standard-normal test statistic) into a p-value for a one- or two-tailed hypothesis test, then see it visualised as the shaded tail area on the standard normal curve. The smaller the p-value, the stronger the evidence against the null hypothesis — reject H₀ when p drops below your significance threshold (commonly 0.05). | 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. |