Crystal Ball uses three types of data cells as inputs and outputs:
Assumption cells are input cells that contain values that you are unsure of: the uncertain independent variables in the problem you are trying to solve. The assumption cells must contain simple numeric values, not formulas or text.
Decision variable cells are input cells that contain values that are within your control to change. The decision variable cells must contain simple numeric values, not formulas or text. These are used by some of the Crystal Ball tools and by OptQuest.
Forecast cells (dependent variables) are output cells that contain formulas that refer to one or more assumption and decision variable cells. The forecast cells combine the values in the assumption, decision variable, and other cells to calculate a result. A forecast cell, for example, may contain the formula =C17*C20*C21.
Every Crystal Ball model must contain at least one assumption and forecast. Decision variables are optional for basic simulations.
Assumptions can have a range of values, defined with probability distributions (About Assumptions and Probability Distributions).
The topics about assumptions provide step-by-step instructions for defining assumption cells in Crystal Ball models so simulations can be run against them. They also describe how to use the Distribution Gallery to organize favorite distributions and define categories of distributions to share with others.
If you are a new user, consider working through Tutorial 1 in Crystal Ball Tutorials, before you read these topics.