I believe the answer is: The control group would be cars that were washed by hand
The control group exist in order to measure the result that created by subjects that recieve specal treatment (the special treatment in this case would be the automated car wash).
In the example above, the result from automatic car wash would be controlled by comparing it to the result from handwashed cars.
"The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people." The federal government is another name for the national government (Congress, the President, and the Supreme Court) of the United States.
The problem starts already earlier:wildlife experts can only estimate the number of species in the world generally!
This is the case because there are simply too many species, and it takes time to documents them; because some areas (ocean bottom for example) are very hard to access and because sometimes it's hard to know whether we're talking about a new species or a variation within the same species.
so if we even don't know how many species there are, it's even harder to know how many are endangered.
Negative reinforcement and positive reinforcement
