Do-VemberScientists experiment. They change the variables and see what happens. What's the optimum range for whatever? How much is too much, what amount is just enough, and how much margin do you have? This kind of testing goes on all the time, everywhere from high-tech labs testing pharmaceuticals, to parents figuring out how long a child's afternoon nap should be or how many toys are enough without being too many, to the people who figured out that Ted Talks should be exactly 18 minutes long.
Sometimes it's nice when someone else does the work for you. If you trust their reporting, it could save you having to reinvent the wheel, or, as in today's Pinterest link, the cake and the cookie. What happens if you put in one egg? Two? Three? How do cookies change if you use white sugar? brown sugar? Some other sweetener? Butter, margarine, or some other kind of fat? You may have seen magazine articles illustrating this before (I have one stuck in my recipe binder that shows different oatmeal cookie results), but the post linked on Pinterest has collected up a few useful ones. It's helpful when the muffins turn out tough or pointy, or the cookies spread too much. Like a scientist, you can ask: what caused that? What do I need to change?
This kind of experimenting is actually something that Charlotte Mason wanted her students to practice--within reason, as they didn't want to waste food on things that wouldn't work. There were times when you might want your little cakes to be richer, or sweeter, or have some other special quirk--so knowing how to adjust a recipe for taste or ingredients was a useful thing to learn. If I were teaching that to children now, I think I'd use muffins as an example: there's a basic formula (I took mine from The Tightwad Gazette years ago), but the special ingredients, amount of sweetener, amount of fat and so on can be up to the baker. Sometimes you can take advantage of a material's particular quirks: a non-food example would be strips of crocheting that tend to curl and twirl around themselves. That can be a problem, but if you're making legs for an octopus, it's exactly what you want.
But it can be useful just to see someone else's results.