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Both calculators run independently — change the inputs on either side to compare results.
Cohen's d Effect Size Calculator
Calculate Cohen's d — the standardized difference between two group means in pooled standard deviation units. Measures how big an effect is, not just whether it is significant.
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
| Cohen's d Effect Size Calculator | P-Value Calculator | |
|---|---|---|
| Category | Statistics | Statistics |
| Inputs required | 4 | 2 |
| Result | Cohen's d | p-value |
| What it does | Calculate Cohen's d — the standardized difference between two group means in pooled standard deviation units. Measures how big an effect is, not just whether it is significant. | 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). |