What is RMSE?

RMSE is a way to see how close your guesses are to the real answers, like when you're trying to find out how many jellybeans are in a jar.

Imagine you and your friend are both guessing how many jellybeans are in a big glass jar. The person whose guess is closest to the actual number of jellybeans wins. That’s kind of what RMSE does, but for numbers instead of jellybeans.

Let’s say you guessed 20 jellybeans, and there were actually 25. Your guess was off by 5. If you did that several times, guessing the number of jellybeans in different jars, you could add up all those differences to see how good your guesses are overall.

But RMSE takes it one step further: It squares each difference (so 5 becomes 25), adds them all together, and then finds the average. Finally, it takes the square root so we’re back to something that looks like a regular difference, but this time, it’s an average of how much you're off.

That way, RMSE gives us a clear picture of how accurate our guesses are on average, just like knowing whether your jellybean guessing is pretty good or needs some practice. RMSE is a way to see how close your guesses are to the real answers, like when you're trying to find out how many jellybeans are in a jar.

Imagine you and your friend are both guessing how many jellybeans are in a big glass jar. The person whose guess is closest to the actual number of jellybeans wins. That’s kind of what RMSE does, but for numbers instead of jellybeans.