Stratified sampling is a probability-based method where the population is separated into meaningful subgroups, or strata, according to shared characteristics, and random participants are then selected from each subgroup (Health Knowledge, n.d.). For a study of vaccination rates across a large metropolitan area, stratified sampling offers a systematic and rigorous means to ensure that all important segments of the population are represented.

To implement stratified sampling for this study, I would begin by identifying key variables that may influence vaccination rates such as age, socioeconomic status, race or ethnicity, and geographic area. Because these characteristics are often linked to differences in vaccine access and uptake. Stratified sampling uses such variables to partition the population into subgroups before sampling so that each group is appropriately represented (Hayes, 2025). For example, subgroups could include Hispanic/Latino, Black/African American, White, and Asian residents, further organized by regional ZIP-code clusters (north, south, east, and west). Once each subgroup is clearly defined and the proportion of the city's population within each is calculated, participants would be randomly selected from every stratum using proportional allocation. This ensures that the final sample accurately mirrors the distribution of the community.

The rationale for this sampling design is strongly supported in methodological research by using stratified sampling, all important subgroups are represented, which allows for detection of differences in vaccination rates across demographicand geographic lines (Reddy & Khan, 2023). Since vaccine access and uptake often vary by race, ethnicity, and place of residence, stratifying by those factors enhances the likelihood of identifying disparities (Howellet al., 2020). Furthermore, a stratified random sampling approach tends to lower sampling error and improves the precision of estimates when compared with a simple random sampling method (Simkus, 2023).

References

Hayes, A. (2025). How Stratified Random SamplingWorks, With Example. https://www.investopedia.com/terms/stratified_random_sampling.asp

Health Knowledge. (n.d.). Methods of sampling from a population. https://www.healthknowledge.org.uk/public-health-textbook/research-methods/1a-epidemiology/methods-of-sampling-population#:~:text=Stratified%20sampling%20improves%20the%20accuracy,into%20account%20in%20the%20analysis

Howell, C. et al. (2020). Area based stratified random sampling using geospatial technology in a community-based survey. https://pmc.ncbi.nlm.nih.gov/articles/PMC7653801/

Reddy, K. & Khan, M. (2023). Constructing efficient strata boundaries is stratified sampling using survey cost. https://pmc.ncbi.nlm.nih.gov/articles/PMC10641212/

Simkus, J. (2023). Stratified Random Sampling : Definition, Method, & Examples. https://www.simplypsychology.org/stratified-random-sampling.html

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