Compare calculators
Both calculators run independently — change the inputs on either side to compare results.
Number Needed to Treat (NNT) Calculator
Calculate the number of patients who must be treated to prevent one additional bad outcome, from the control and treatment event rates. A key measure of clinical effectiveness.
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.
Key differences
| Number Needed to Treat (NNT) Calculator | P-Value Calculator | |
|---|---|---|
| Category | Statistics | Statistics |
| Inputs required | 2 | 2 |
| Result | Number Needed to Treat (patients) | p-value |
| What it does | Calculate the number of patients who must be treated to prevent one additional bad outcome, from the control and treatment event rates. A key measure of clinical effectiveness. | 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). |