In Groves and Heeringa's original formulation, responsive design proceeds in phases. They define these phases as:
"A design phase is a time period of a data collection during which the same set of sampling frame, mode of data collection, sample design, recruitment protocols and measurement conditions are extant." (page 440).
These responsive design phases are different than the two-phase sampling defined by Hansen and Hurwitz. Hansen and Hurwitz assumed 100% response so there was no nonresponse bias. There two-phase sampling was all about minimizing variance for a fixed budget.
Groves and Heeringa, on the other hand, live in a world where nonresponse does occur. They seek to control it through phases that recruit complementary groups of respondents. The goal is that the nonresponse biases from each phase will cancel each other out. The focus on bias is a new feature relative to Hansen and Hurwitz.
A question in my mind about the phases is how the phase boundaries should be defined. In Groves and Heeringa, they are points in time. Even saying which points in time is difficult. Groves and Heeringa suggest the use of the concept "phase capacity":
"Phase capacity is the stable condition of an estimate in a specific design phase, i.e. a limiting value of an estimate that a particular set of design features produces." (p. 445).
Deciding when this has occurred is an interesting statistical problem in its own right. There are a couple of articles on stopping rules which may be relevant for formalizing these definitions of phase boundaries.
I'm interested in designs where phase boundaries may be something other than a point in time. In my dissertation, I tried to show the adaptive treatment regimes approach might be applied to surveys. These regimes adapt the treatments to the baseline characteristics and history of previous treatments. Could this be thought of as an extension of responsive design? I think it might, if the concept of phases can be extended to include boundaries identified at the case level."Phase capacity is the stable condition of an estimate in a specific design phase, i.e. a limiting value of an estimate that a particular set of design features produces." (p. 445).
Deciding when this has occurred is an interesting statistical problem in its own right. There are a couple of articles on stopping rules which may be relevant for formalizing these definitions of phase boundaries.
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