Researchers compare the body composition of cattle feeding on a grain diet with that of cattle feeding on a grass diet. This

Question

Researchers compare the body composition of cattle feeding on a grain diet with that of cattle feeding on a grass diet. This method of gathering data is classified as
(1)a census.
(2)a sample survey
(3)an experiment.
(4)an observational study.

Kunduz · Accepted Answer

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