Aresearcher wants to know why individuals in community a have a higher rate of a rare form of cancer when compared to those living in community b. to find out the reasons for the differences their lifestyle, noted the types of businesses that were present in the community and sea medical records. the researcher found that the headquarters for the toxico chemical plant is located in community a, there is a higher rate of cigarette smoking in this community and residents tended to delay or skip going to the doctor for an annual checkup. in community b, the largest employer was a department store and on average, residents did not smoke as much as residents from community a. however, like individuals from community a, community b residents tended to delay or skip their annual checkup with their doctor. in cancer rates in these two communities, the investigator surveyed residents about rched 11) suppose community a was a warmer climate than community b.

how might this introduce a confounding variable that the researcher did not consider at first?