Discover why over-representation of health-conscious volunteers in a lifestyle study exemplifies selection bias, with detailed explanations and examples for exam preparation.
Table of Contents
Question
An example of selection bias in a study would be
A. Random errors in data entry
B. Over-representation of volunteers who are health-conscious in a lifestyle study
C. Participants mistakenly recalling their past behaviors
D. Varying responses due to the interviewer’s tone of voice
Answer
B. Over-representation of volunteers who are health-conscious in a lifestyle study
Explanation
Explanation of Selection Bias
Selection bias occurs when the study population systematically differs from the target population due to non-random sampling or recruitment methods, leading to distorted results12. This bias undermines the validity of research by introducing unrepresentative samples.
Why Option B is Correct
Volunteer/self-selection bias is a common type of selection bias. Health-conscious individuals are more likely to volunteer for lifestyle studies, creating an over-representation of healthier habits in the sample.
For example, a study on diet and heart disease that recruits health-focused volunteers would misrepresent the general population’s dietary habits, skewing associations between diet and health outcomes.
Why Other Options Are Incorrect
A. Random errors in data entry: These are unrelated to sampling and reflect measurement errors, not systematic bias.
C. Participants mistakenly recalling past behaviors: This is recall bias, a type of information bias affecting data accuracy, not sample selection.
D. Varying responses due to interviewer’s tone: This is interviewer bias, influencing responses rather than participant selection.
Key Takeaway
Selection bias often stems from flawed recruitment (e.g., relying on volunteers or excluding subgroups). Recognizing it is critical for designing studies that generalize accurately to broader populations.
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