Rolling two dice has 36 outcomes, which you can calculate in Excel by entering "=6*6" without quotes, because you have two dice, each with six sides. Enter the number of positive outcomes in cell A2.

In Excel, syntax for this function is NORMINV (probability,mean,standard deviation). Using the sales example, with a weekly sales average of $2,000 that fluctuates about $500 up or down, you know ...