Imagine that your in charge of armoring United States Air Force planes as they perform routine missions to Germany. You obviously want to keep the pilots and the planes safe as they go on these missions. As the planes are in production, you decide to armor the planes with a uniform thickness and weight.

After a few months, you get some results of your planes returning. The data represented below is what you find:

Now, what would you do with this data? Seriously... think about it...
Clearly the armoring in the planes does not need to be uniform. In fact, there are some areas that could be armored more. But, where are these areas? Before you jump at your answer, consider a critical piece of data that is not necessarily given to you: what about the planes that DIDN'T return? Wouldn't it make sense then to fortify the armor in the areas where there is no data?