What are Confounding Variables?

Any variable that has effects on both the independent and dependent variable in statistics is a confounder. In many cases, research works never account for confounders. Confounders normally increase variance an at the same time help in introducing bias in the experiment. There are at least three conditions that must exist for confounders to take effect in any statistical research. The conditions include the fact that the confounder must have an association with the risk factor in question as well as the outcome of the experiment, there must be unequal distribution of the confounder among the groups under comparison, and the fact that a confounder is not an intermediary step in the experiment all the way from the exposure to outcome of the interest under study in the experiment or research ( Cleophas & Zwinderman, 2012).  

Education highly reduces coronary heart diseases according to research as those with education according to several research findings are safe from heart diseases given their levels of knowledge on the same. However, in such research findings there are potential confounding factors that come into play. The inverse association between education and coronary heart disease is not clear whether it is purely due to schooling effects or whether some potential confounding factors prior to schooling influence the same. This make such kind of a research have inconsistencies and bias. There are early life potential confounders that many research work ignore yet the same affect the association that exists between education and coronary heart diseases. Issues such as childhood intelligence in one way or the other affect how one grows up and performs in education yet such factors do not form major parts of the research. It is common knowledge that unless one is intelligent from childhood then definitely the person may struggle later in academics but then again how is this association plugged into the coronary heart disease issue and if such is plugged then it changes the scenario in many ways. Maternal mental health, illnesses at childhood as well as the economic circumstances that one faces at childhood are all potential confounding factors of early life that in one way or the other have a connection with the coronary heart disease and thus just stating the word education is not enough in some instances. 

Reference 

Cleophas, T. J., & Zwinderman, A. H. (2012).  Statistics applied to clinical studies . Dordrecht: Springer.