The factor that a scientist changes in a controlled experiment is the _____________

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http://docs.google.com/viewer?a=v&q=cache:a3oR3szBgXgJ:infohost.nmt.edu/~klathrop/controlled_experimnet.pdf+factor+that+a+scientist+changes+in+a+controlled+experiment&hl=en&gl=us&pid=bl&srcid=ADGEESgTKKdnPW0dtQA0PsieUJh6uoRTnd6bWOOXUffxjIn1iGMOR8BRpgBNY_1XaGHJQ7yAo30q1IdLWju3aMbOxJRhlpp_5ckg8Ky8qFrhNKQOB-OdC6FErio-_2gaLKebbYiNwkYm&sig=AHIEtbQQHZWPb73ZEbckGIRLIF3Or2NsIA