Sample Size

Another way to think about sample size is how certain you want to be about your results. Let's say you're coaching a baseball team, and you see a young pitcher throw a 100 mph fastball. "Wow, that's fast!" you think.

But before you hire him, don't you want to see him do it again? And again?? The more times you see him throw a 100 mph fastball, the more certain you are that he can do it again. You probably wouldn't think he's so hot if he could only throw like this once a year!