In which dialog do you specify the variable cells when using Solver?

The Solver Parameters dialog is the essential interface for defining and configuring the problem that Solver will address. In this dialog, you specify the variable cells, which are the cells that Solver will adjust in order to obtain the desired outcome based on your defined objective. This is a crucial step because the variable cells represent the decision variables that Solver manipulates to optimize the model according to the constraints and objectives you set.

Choosing this dialog allows you to define not only the variable cells but also the target cell (objective function) and the constraints that must be adhered to during the optimization process. It serves as the core area where all fundamental components related to the solving process are set up, making it the most critical dialog for using the Solver tool effectively.

In contrast, other dialogs mentioned serve different purposes. The Data Validation dialog is used for setting rules about data entered into cells, the Scenario Values dialog helps in changing values for different scenarios but doesn't handle optimization processes, and the Add Constraint dialog is specifically for introducing constraints to the optimization problem rather than defining the variable cells. Therefore, the Solver Parameters dialog is unequivocally the correct choice for specifying variable cells.