This study is a correlational study. Nothing is manipulated by the researchers. They are essentially looking to see how sugar intake and number of cavities covary. As this is a corrleational study, there is no independent or subject variable; we do not know what is responsible for the covariation and nothing is manipulated. While on the surface, it would appear that the researcher draws a valid conclusion, this is not the case. In a correlational study, one can not make cause and effect statements. We do not know if sugar causes cavities, if individuals prone to cavities crave sugar, or if some other variable is involved.
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