Confounds are variables that provide an alternate explanation because they change along with the independent variable. That is, one level of the independent variable is always associated with one level of the confounding variable. In this example, identify a confounding variable:
A nutritionist is investigating the effects of eating oatmeal for breakfast. He asks all of his participants to eat about 350 calories for breakfast every day for six months. He assigns the experimental group to eat oatmeal with honey. He asks the control group to eat anything other than oatmeal and honey. He then tests their blood levels for cholesterol and other substances.