๐งช P-Value Calculator
The p-value is the probability of seeing a result at least this extreme if nothing were really going on. From your z-score, this calculator finds the two-tailed area under the bell curve โ the standard yardstick of statistical significance.
The usual bar is p < 0.05: below it, researchers call the result statistically significant; above it, the evidence is too weak to rule out chance. The calculator labels your result against the 1%, 5% and 10% levels automatically.
How to use this calculator
Type your z-score and press Calculate for the two-tailed p-value and its significance reading.
- Type the z-score from your test.
- Press Calculate.
- Read the two-tailed p-value.
- Check the interpretation line for the 1, 5 and 10 percent significance levels.
Frequently asked questions
What does this p-value calculator compute?
It converts a z-score into a two-tailed p-value using the standard normal distribution, via a precise error-function approximation, and labels the result against common significance levels.
Can you show a worked example?
A z-score of 1.96 gives a p-value of 0.05, significant at the 5 percent level. A z of 2.576 gives 0.01, highly significant. A z of 0 gives exactly 1.
What does the p-value actually mean?
It is the probability of seeing a result at least this extreme if there were really no effect. Small values argue against that no-effect explanation; they are not the probability that your hypothesis is true.
Why two-tailed?
Two-tailed counts extremes in both directions, the standard default when you did not predict the direction in advance. A one-tailed value for the same z would be exactly half.