In my probability course I encountered a difficult problem that required looking at two variables at the same time. I was analyzing a software program that had two different modules. I needed to track the number of errors in Module 1 (variable X) versus the number of errors in Module 2 (variable Y). That assignment taught me that looking at one variable in isolation often hides the real story. I built this calculator to handle those complex "X and Y" scenarios where you need to check if two events are truly independent or if they influence each other. For example I had to calculate if a bug in the first module made it more likely to find a bug in the second module.