Experimentation means where you can control one variable, right? Social psychology?

do you have any examples that can help me understand experimentation ?Experimentation means where you can control one variable, right? Social psychology?
Coke and Pepsi taste tests can be good examples of this. Let's say that Coke invents a new product Super Coke(SC). To determine if SC tastes better than Pepsi, equal amounts of each beverage will be poured in unmarked cups. The cups should have a number under them to identify each product. Then someone who is unrelated to the expermint will come in, put the cups on a tray and serve them to test subjects. The test subjects will just know this is a taste test and have no idea if it's Coke, Pepsi, etc.





This is called a double blind expermint, where the subject has no idea which one he/she just tasted, and the person who served the beverage has no idea which one is which. The only way to identify SC from Pepsi is the number (should be in form of barcode for further confusion) on the bottom of the cup.





This expermint avoids any bias from the test subject, who might favor Pepsi over coke, therefore no matter how good the Coke tasted would choose Pepsi. Avoids any bias from the server who also may be biased and try and influnce the result by smiling when serving Coke and acting badly when serving Pepsi.





Now replace Coke and Pepsi with a known medication and a new medication or a placebo and then the results of the medication can accurately be determined.Experimentation means where you can control one variable, right? Social psychology?
A proper experiment will only have one thing that can cause the change. this means that when something changes, you know it is a direct result of that one variable.