Confounding is the term used to describe distortion of the estimate of the effect of an exposure of interest because it is mixed with the effect of an extraneous factor. According to Susser, a confounding variable is “an independent variable that varies systematically with the hypothetical causal variable under study. When uncontrolled, the effects of a confounding variable cannot be distinguished from those of the study variable” (Friis & Sellers, 2014, pg. 445).

In your Week Five assignment, please answer the following questions:

- Define confounding and state how confounding can affect a study’s conclusion. What is meant by Simpson’s paradox and how does it pertain to confounding? How do epidemiologic researchers control for confounding?
- Suppose as an epidemiologist you are responsible for measuring study participants’ blood pressure. Some dropped the instrument and the needle on the gauge has been bent so that the readings are too high. What type of error is this? What type of error would occur if the instrument is working properly but only one person took only measurement from each person? How could you minimize each of the foregoing types of error?

Consider the following scenario to answer questions c through h: The death rate per 100,000 for lung cancer is 7 among nonsmokers and 71 among smokers. The death rate per 100,000 for coronary thrombosis is 422 among nonsmokers and 599 among smokers. The prevalence of smoking in the population is 55% (If necessary, refer to the chapter 9 on cohort studies for formulas for relative risk (RR) Be sure to show the formulas for your work as well as your calculations. Present your final results and their interpretation in a table format.

- What is the RR of dying of lung cancer for smokers versus nonsmokers?
- What is the RR of dying of coronary thrombosis for smokers versus nonsmokers?
- Ws the etiologic fraction of disease due to smokihat ing among individuals with lung cancer?
- What is the etiologic fraction of disease due to smoking among individuals with coronary thrombosis?
- What is the population etiologic fraction of lung cancer due to smoking?
- What is the population etiologic fraction of coronary thrombosis due to smoking?
- Determine whether or not the interpretation of the study results could be subject to bias.