An investigator found an association between beta carotene consumption and reduced risk of colon cancer. But it was found that it may be also due to increased fiber in such diets. Such a kind of occurrence is termed-

Ans. is 'b' i.e., Confounding factor Confounding is considered a mixing of effects. When a factor 'X' causes a disease 'Y', and relationship could be confounded by a factor 'C' that is associated with both factor 'X' and disease Y. 'C' would be an alternative explanation for the relationship observed between 'X' and 'Y', i.e., C is acts as confounding factor (read below). Here beta Carotene Consumption reduces risk of colon cancer; however, it is confounded by increased fiber intake.