There is no litmus test a spreadsheet must pass to be considered a "what if" model. The term is generic and refers to a number of different types of spreadsheets. Any spreadsheet you design that allows you to experiment with input values can be considered a "what if" model. This concept will look at three specific types of "what if" models. While not a comprehensive treatment of "what if" models, the discussion should provide you with enough information that you can begin to use "what if" models in your own work.
The simplest type of "what if" model is a spreadsheet that shows the impact of changing one value. There may be multiple results and complex calculations inside the spreadsheet, but the spreadsheet is designed to show the effects of changing one value.
Another type of "what if" model is that which has multiple input values and shows the relationships between values, or how different value pairs affect the domain which is being simulated.
The third type of "what if" model to be considered here is one that helps you search for the optimal value. Rather than manually entering the input values for each variation, you can copy the simulation several times and create a formula or function that computes the input values for each copy based on the value of the input and result for the previous simulation. If you need to change the input value by a random amount, the RAND function can be used. The RAND function returns a random number between 0 and 1.