All of creation is an experiment.
As far as the one supreme being thing, I would say it is a lot more complicated than this.
Basically humanity is a collection of hybrid aliens, and if we are an experiment, than there are multiple species that are fighting over us.
What I will tell you is that one of these species is the Anunnaki or elohim.
I guess the game is up, you guys got me. Anyway, time to start a new universe. By the way, while I was here I loved the tacos. They were delicious- I knew you guys weren't a waste of time. Then again I have all the time I want so it doesn't matter. Later guys...
Other beings who are more advanced in technology/intelligence and at some point were traveling through the universe doing their research could have created humanity. A human is an ape with enhanced genetics/intelligence. It is easier for people to accept there are gods or holy creatures rather than accept being an animal lab rat. Our creative intellectual part is always in unbalance with animal instinct part. Science has proven all life on earth shares the same bacterial ancestor, so if everything was evolving equally from one thing isn't it strange that only one species nowadays have such advantage in intellect and are dominating everything else?
Whether or not there is a supreme being is something that can be debated. However, humanity clearly was not "created." Humanity is the product of evolution, as is all the other life on this planet. This is something clearly supported by the scientific process of that is back by evidence.
It's possible, but fewer and fewer people are entertaining the idea because there's so little to indicate it being a real possibility. Humanity appears to be the one known occurrence of everything going right in the formation of a universe, there may be more but some scientific studies looking at multiple sun systems and etc make it seem like a very rare happening.
Humans are not controlled by a supreme being and part of a large experiment because to do so would limit our free will. The idea of free will is instilled and part of any line of thought that involves a supreme being. If we were part of an experiment then that implies this being would be an active member in our lives that then limits our free will.
The idea that there is a supreme being that created the earth and universe is essentially pointless. There as been no clear indication that this being exists and given the fact that scientists have been able to unlock almost all the secrets of the universe, it seems that they would have stumbled upon the markings of someone else by now.