P-Value Calculator
Turn a test statistic into a p-value and see if the result is statistically significant.
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P-value
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What a P-Value Means
The p-value is the probability of seeing a result at least as extreme as yours if the null hypothesis were true. A small p-value (below α, often 0.05) is evidence against the null hypothesis.
Two-tailed p = 2 × min(CDF(x), 1 − CDF(x)) Right-tailed p = 1 − CDF(x)
The t distribution uses the regularized incomplete beta function (accurate to many decimal places).
Worked Example
Tips
A p-value isn’t the chance the null hypothesis is true, and "not significant" doesn’t prove there’s no effect. Report effect sizes and confidence intervals too.