p-value
The p-value of a hypothesis test is the smallest value of alpha (significance
level) that would lead to rejection of the null hypothesis. It is the observed
level of significance.
A small p-value provides evidence in support of the alternative hypothesis.
In practice, the analyst sets the desired level of significance to, say, 5%.
If the observed significance level (the p-value) is less than the desired
level of significance then the null hypotesis can be rejected.
For instance, following the example under concept "One-side tests" (on real
estate) the p-value is the probability
p-value = P(z > 1.932) = 0.0316
For a given significance level of 5%, the observed p-value of 0.0316 indicates
that the null hypothesis can be rejected. It can even be said that there is
a 3.16% probability of making a mistake by rejecting the null hypothesis
(less than the tolerated level of 5%).