Q20. Which of the following pairs correctly identifies the independent and dependent variables in a dental whitening study? A) Independent variable:Toothpaste brand; Dependent variable: Gum health B) Independent variable:Age; Dependent variable Tooth sensitivity C) Independent variable Frequency of brushing;Dependent variable: Tooth color D) Independent variable:Gender, Dependent variable.Dental plaque accumulation

The correct answer is C) Independent variable: Frequency of brushing; Dependent variable: Tooth color.<br /><br />In a dental whitening study, the independent variable is the frequency of brushing, as it is the factor that is manipulated or controlled by the researcher. The dependent variable is the tooth color, as it is the outcome or response that is measured or observed in the study. The tooth color is dependent on the frequency of brushing, making it the dependent variable.