Mathematics · Glossary
What is P-Value?
Quick definition
The probability of observing results at least as extreme as those observed, assuming the null hypothesis is true.
Full explanation
A p-value is the probability, under a specified statistical model (the null hypothesis), of obtaining a result equal to or more extreme than what was actually observed. A p-value of 0.03 means: if there is no real effect, there is a 3% chance of seeing data this extreme by random variation alone. The conventional threshold is p < 0.05 to declare "statistically significant." P-values do NOT measure the probability that the hypothesis is true, nor the size of an effect. They are widely misunderstood. Replication and effect size matter at least as much. The American Statistical Association has published warnings about p-value misuse.
Related calculators
Calculators that use or explain P-Value.
Related terms
More from Mathematics
Standard Deviation
A measure of how spread out numbers are from their mean. Low = consistent, high = volatile.
Mean (Average)
The sum of values divided by the count. The most common type of "average." Sensitive to outliers.
Median
The middle value in a sorted list. Half the values are above, half below. Robust to outliers.
Pythagorean Theorem
In a right triangle, the square of the hypotenuse equals the sum of the squares of the two legs: a² + b² = c².
Logarithm
The exponent to which a base must be raised to produce a given number. log(100) = 2 means 10² = 100.
Exponent
A number that indicates how many times a base is multiplied by itself. 2³ = 2×2×2 = 8.
Last reviewed: June 15, 2026 • Category: Mathematics