Uses of Excel

Whether you are new to Excel or you have some experience there are always new things that can be learned, especially when using Excel for decision-making in your personal life or business. How could you use Excel in your personal, educational or professional lives to improve decision-making?
Provide an example of where you did or could have used a spreadsheet to aid your decision-making.  Describe the scenario and the types of questions you could answer with the spreadsheet.