The probability that a variate would assume a value greater than or equal to the observed value strictly by chance: 
.
P-Value
See also
Alpha Value, Hypothesis Testing, SignificanceExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "P-Value." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/P-Value.html