### Responsive Design Phases

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.

### "Responsive Design" and "Adaptive Design"

My dissertation was entitled "Adaptive Survey Design to Reduce Nonresponse Bias." I had been working for several years on "responsive designs" before that. As I was preparing my dissertation, I really saw "adaptive" design as a subset of responsive design.

Since then, I've seen both terms used in different places. As both terms are relatively new, there is likely to be confusion about the meanings. I thought I might offer my understanding of the terms, for what it's worth.

The term "responsive design" was developed by Groves and Heeringa (2006). They coined the term, so I think their definition is the one that should be used. They defined "responsive design" in the following way:

1. Preidentify a set of design features that affect cost and error tradeoffs.
2. Identify indicators for these costs and errors. Monitor these during data collection.
3. Alter the design features based on pre-identified decision rules based on the indi…

### An Experimental Adaptive Contact Strategy

I'm running an experiment on contact methods in a telephone survey. I'm going to present the results of the experiment at the FCSM conference in November. Here's the basic idea.

Multi-level models are fit daily with the household being a grouping factor. The models provide household-specific estimates of the probability of contact for each of four call windows. The predictor variables in this model are the geographic context variables available for an RDD sample.

Let $\mathbf{X_{ij}}$ denote a $k_j \times 1$ vector of demographic variables for the $i^{th}$ person and $j^{th}$ call. The data records are calls. There may be zero, one, or multiple calls to household in each window. The outcome variable is an indicator for whether contact was achieved on the call. This contact indicator is denoted $R_{ijl}$ for the $i^{th}$ person on the $j^{th}$ call to the $l^{th}$ window. Then for each of the four call windows denoted $l$, a separate model is fit where each household is assum…

### Is there such a thing as "mode"?

Ok. The title is a provocative question. But it's one that I've been thinking about recently. A few years ago, I was working on a lit review for a mixed-mode experiment that we had done. I found that the results were inconsistent on an important aspect of mixed-mode studies -- the sequence of modes.

As I was puzzled about this, I went back and tried to write down more information about the design of each of the experiments that I was reviewing. I started to notice a pattern. Many mixed-mode surveys offered "more" of the first mode. For example, in a web-mail study, there might be 3 mailings with the mail survey and one mailed request for a web survey. This led me to think of "dosage" as an important attribute of mixed-mode surveys.

I'm starting to think there is much more to it than that. The context matters  a lot -- the dosage of the mode, what it may require to complete that mode, the survey population, etc. All of these things matter.

Still, we ofte…