A municipal survey with a frame gap
A Korean municipality wants to estimate residents’ satisfaction with a new public service. The team has a list of registered household addresses, but its initial plan is to post a voluntary questionnaire only on a social-media page followed mainly by younger residents. An officer argues that two thousand online replies will automatically be more representative than a smaller probability sample. The intended population includes residents who do not use that platform, and the service is used differently across age groups. No administrative rule requires the proposed online-only design. Before recruitment, the team must define the target population, choose a defensible selection method and decide what the eventual conclusions can legitimately describe.
1. Why is response count alone insufficient?
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An opt-in platform sample can under-cover residents and select people with unusually strong interest. Increasing its size does not automatically remove those selection mechanisms.
2. Propose a defensible improvement.
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Use an appropriate population frame and probability design, with accessible contact modes and documented follow-up. Compare achieved coverage and response patterns with the intended population before interpreting estimates.