Several scientists are working together to study the change in the number of whales born each year along the northern coast of california. what is the controlled parameter

I believe that in this case the controlled parameter is the type of animal that they are observing. There are a lot of animals in the ocean, therefore to have a scope of their study of observation, they are controlling or limiting their observations on the whale alone. Hence the controlled parameter is the type of animals, whales.

10 years is the answer

answeridentity;