Math
P-value Calculator
Convert a z-score to a p-value for one- or two-tailed tests with significance verdict.
Inputs
P-value Calculator
Result
p-value
4.9996e-2
- Also written
- 0.049996
- α = 0.05
- Significant ✓
- α = 0.01
- Not significant
How it's calculated
Two-tailed p = 2·(1 − Φ(|z|)). Φ uses the Abramowitz–Stegun erf approximation.
Common questions
What is a p-value?
The probability of observing a test statistic at least as extreme as the one measured, assuming the null hypothesis is true.
Is p < 0.05 always meaningful?
Statistical significance doesn't imply practical significance — always consider effect size and context.
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