# OAT design in {{uranie}}

In {{uranie}}, each factor of the OAT design takes at least three values: a *nominal value*, a 
*lower value* (smaller than the nominal one) and an *upper value* (greater than the nominal one). 
When a factor is not "modified" it is set to its nominal value.  This leads to a design of $2n+1$ 
experiments, where $n$ is the number of factors, and "$+1$" refers to a reference experiment, where 
no factor is modified.

Two classes can produce OAT designs:

- **`TOATSampling`:** simple, but limited in its functionality. It is used by some classes of 
{{uranie}}.

- **`TOATDesign`:** an improved version of the previous one, more user oriented.

As **`TOATSampling`** will become deprecated in a future version of {{uranie}} the present document 
will focus on the usage of **`TOATDesign`**.