Response 1 Discussion: Association and Bias in Observational Studies


Hypothetical Study: Does hot tub use increase the risk of contracting Legionnaires’ Disease?

Types of possible bias in this study: I feel selection bias may occur during this study as one of my exclusion criteria is to forgo the enrollment of those considered high-risk for contracting Legionnaires’ Disease. Due to this selection bias, high-risk individuals “may not have enjoyed a similar opportunity and thus would not be represented in the study” (Friis, 2021). Another form of bias that may be introduced into this study is prevarication bias, which may lead to the skewed results. If an unequal number of individuals are represented in each group (hot tub users vs hot tub users), this may “exaggerate exposures” (Friis, 2021). Prevarication bias is a type of information bias.

Causal relationships: As indicated in the question for the study, there is a potential causal relationship between hot tub use and the contraction of Legionnaires’ Disease. If the number of cases in individuals who did use hot tubs frequently is higher than those who do not use hot tubs, this would certainly lend credibility and evidence to a causal relationship.

Measures of Significance: I feel that the statistical measures of significance would include the use of P values in order to minimize the odds that an individual’s Legionnaires’ Disease from other sources of water. In turn, this would help establish the clinical significance depending on the sample size.

Confounding Variables: I feel that a confounding variable to this experiment would be the synonymous use of a pool or sauna during this experiment as it would be nearly impossible to discern which water source contributed to the contraction of Legionnaires’ Disease. Additionally, another confounding variable would be exposure to someone with pneumonia, which may result in the participant experiencing symptoms that may be misleading to the conclusion that they have contracted Legionnaires’ Disease.

I feel that a method to control my first confounding variable would be to expressly prohibit the use of pools and saunas while participating in the study. Although it may be impossible to fully prevent exposure to my second variable, I feel that participants may receive a pneumococcal vaccine in order to prevent contracting a stain of pneumonia that is not Legionnaires’ Disease.

Friis, R.H., & Sellers, T.A. 2021. Epidemiology for public health practice (6th ed). Jones & Bartlett Learning.