Z-Score to P-Value Calculator
Convert z-scores to p-values and determine statistical significance.
Calculate P-Value from Z-Score
Table of Contents
What is P-Value?
A p-value is a probability measure that helps determine the statistical significance of a result. It represents the probability of obtaining a result at least as extreme as the one observed, assuming the null hypothesis is true.
- Measures statistical significance
- Probability under null hypothesis
- Common threshold: 0.05
- Lower p-value = stronger evidence
P-Value Interpretation
p < 0.05
Statistically significant result
p ≥ 0.05
Not statistically significant
p < 0.01
Highly significant result
p < 0.001
Very highly significant
Tail Types
Two-tailed Both Directions
Tests for differences in either direction. Used when you want to detect any significant difference, regardless of direction.
Left-tailed Lower Values
Tests for significantly lower values. Used when you want to detect if the value is significantly less than expected.
Right-tailed Higher Values
Tests for significantly higher values. Used when you want to detect if the value is significantly greater than expected.
Common Examples
Example 1 Z-Score = 1.96
Two-tailed p-value = 0.05 (borderline significant)
Example 2 Z-Score = 2.58
Two-tailed p-value = 0.01 (highly significant)
Example 3 Z-Score = 3.29
Two-tailed p-value = 0.001 (very highly significant)