Confounding Variables Statistics Example 4
Follow the full solution, then compare it with the other examples linked below.
Example 4
hardA company claims its energy drink improves athletic performance because athletes who drink it run faster. However, the athletes were not randomly assigned — those who drank the energy drink also trained harder. (a) Identify the confounding variable. (b) Explain what 'controlling for' a confounding variable means. (c) How could the study be redesigned?
Solution
- 1 Step 1: (a) Training intensity is the confounding variable — it is associated with both drinking the energy drink and running faster. (b) 'Controlling for' means holding the confounding variable constant — comparing athletes with equal training intensity who differ only in energy drink consumption.
- 2 Step 2: (c) Redesign: randomly assign athletes of similar fitness and training levels to either drink the energy drink or a placebo. Ensure all participants follow the same training programme. Use double-blinding so neither athletes nor testers know who received the real drink.
Answer
(a) Training intensity is the confounder. (b) Controlling for it means comparing athletes at the same training level. (c) Use a double-blind RCT with random assignment, a placebo, and controlled training.
Confounding variables can be addressed through study design (random assignment) or statistical methods (stratification, regression). The best approach combines random assignment with controlling other variables to isolate the treatment effect.
About Confounding Variables
A confounding variable is a third variable that influences both the independent variable and the dependent variable simultaneously, creating a spurious association between them that can be mistaken for a direct causal relationship. Confounders are a major threat to the internal validity of observational studies.
Learn more about Confounding Variables →More Confounding Variables Examples
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