Probability theory and statistics have some commonly used conventions, in addition to standard mathematical notation and mathematical symbols.

The α-level upper critical value of a probability distribution is the value exceeded with probability ${\textstyle \alpha }$, that is, the value ${\textstyle x_{\alpha }}$ such that ${\textstyle F(x_{\alpha })=1-\alpha }$, where ${\textstyle F}$ is the cumulative distribution function. There are standard notations for the upper critical values of some commonly used distributions in statistics:

Common abbreviations include: