A PhD candidate at MIT is studying vaccine hesitancy using a survey of 2,000 adults. The survey overrepresents urban populations, who make up 80% of the city but account for only 60% of respondents. What is the sampling bias percentage favoring urban dwellers?

Tue, 05 May 2026 11:48:05 +0000

**Why a Top MIT Survey on Vaccine Hesitancy Skews Toward Urban Voices—and What It Means for Public Health Insight** In a time when trust in medical institutions faces growing scrutiny, a recent study led by a PhD candidate at MIT has turned attention to how urban populations perceive vaccine hesitancy—offering fresh data from 2,000 adults across the U.S. But behind the numbers lies a subtle but significant sampling bias: urban residents are overrepresented, making up 80% of the city’s population yet only 60% of survey respondents. This imbalance shapes the findings and reveals important insights into both demographic trends and research methodology. ### The Survey’s Design and Hidden Representation Gap The study aims to uncover patterns behind vaccine hesitancy, a critical topic driving public health strategy nationwide. By randomly sampling 2,000 adults from across cities, the researchers uncovered a demographic mismatch: while urban communities host the majority of city dwellers, they represent fewer respondents in the survey. Using simple percentage math, urban participants account for 60% of the sample, even though they make up 80% of the urban population. Subtracting 60 from 80 reveals a 20 percentage point bias—favoring urban voices by one-fifth.