What is a confounding variable?
a. a confounding variable is a response variable that was not considered in a study whose effect cannot be distinguished from a second explanatory variable in the study.
b. a confounding variable is an explanatory variable that was considered in a study whose effect cannot be distinguished from a second explanatory variable in the study.
c. a confounding variable is a response variable that has an effect on the explanatory variable, but it cannot be accurately measured in the study.
d. a confounding variable is the explanatory variable on which a study has been focused.