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### Mixed-Mode Surveys: Nonresponse and Measurement Errors

I've been away from the blog for a while, but I'm back. One of the things that I did during my hiatus from the blog was to read papers on mixed-mode surveys. In most of these surveys, there are nonresponse biases and measurement biases that vary across the modes. These errors are almost always confounded. An important exception is Olson's paper. In that paper, she had gold standard data that allowed her to look at both error sources. Absent those gold standard data, there are limits on what can be done.

I read a number of interesting papers, but my main conclusion was that we need to make some assumptions in order to motivate any analysis. For example, one approach is to build nonresponse adjustments for each of the modes, and then argue that any differences remaining are measurement biases. Without such an assumption, not much can be said about either error source. Experimental designs certainly strengthen these assumptions, but do not completely unconfound the sources of error.

Having said that, gold standard studies, like Olson's, are an important step to test the validity of these kinds of assumptions. It seems that more such studies, focused on disentangling at least two error sources, would be very useful.

### Comments

1. I can recommend the work of my colleague Jorre Vannieuwenhuyze. He laid out several methods to disentangle such errors. http://scholar.google.nl/citations?user=ekOuDiwAAAAJ&hl=nl

2. Thanks! I'm familiar with his work. My point is that we need some assumptions to motivate any such method. There isn't any magic available!

### "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…