It's important to check the results from an experiment. Does the result make sense? Does it follow from other facts that are known? From the standpoint of teaching High School science, checking if one's results are sensible adds an additional layer of safety that the results are correct. (From the standpoint of advancements in Science, a basic research tenet is that results must be repeatable and not just a fluke. Professional scientists were occasionally discredited when their data can't be replicated; usually, they have made some blunder, but in rare instances, it turns out some aspects of their data has been faked.)

The following story can be used to teach that results must be checked against known facts to see if they're reasonable. It is designed to be a follow up to the PUMAS example "The Fall of the Ruler." Some of the background information in that example is repeated here for ease of understanding.