The text below is taken from Wikipedia article about P-value:
In statistical hypothesis testing, the **p-value** is the probability of obtaining a result at least as extreme as that obtained, *assuming* the truth of the null hypothesis that the finding was the result of chance alone. The fact that p-values are based on this assumption is crucial to their correct interpretation.
More technically, the p-value of an observed value *t*_{observed} of some random variable *T* used as a test statistic is the probability that, given that the null hypothesis is true, *T* will assume a value as or more unfavorable to the null hypothesis as the observed value *t*_{observed}. "More unfavorable to the null hypothesis" can in some cases mean greater than, in some cases less than, and in some cases further away from a specified center. |