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(Pew Research Center illustration)

Survey researchers are frequently interested in measuring changes in public attitudes and behaviors over time. To do so reliably, they try to use the same methodology for every survey. This increases confidence that any observed changes are true changes and not the result of methodological differences. (This earlier Decoded post looks at how researchers can measure changes in public opinion when there has been a change in a survey’s methodology.)

There are many design features that pollsters try to hold constant when measuring trends over time, including question wording, sampling frame, mode of interview, contact procedures and weighting. Probability-based surveys…


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(Pew Research Center illustration)

(Related posts: Introducing pewmethods: An R package for working with survey data, Exploring survey data with the pewmethods R package and Analyzing international survey data with the pewmethods R package)

This post is a companion piece to our basic introduction for researchers interested in using the new pewmethods R package, which includes tips on how to recode and collapse data and display weighted estimates of categorical variables. Here, I’ll go through the process of weighting and analyzing a survey dataset. …


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(Pew Research Center illustration)

(Related posts: Introducing pewmethods: An R package for working with survey data, Weighting survey data with the pewmethods R package and Analyzing international survey data with the pewmethods R package)

The methods team at Pew Research Center regularly works with survey data in R, and we’ve written many functions to simplify daily tasks like cleaning, weighting and analyzing data. The pewmethods R package, available to the public on the Center’s GitHub page, evolved as a way to reuse and maintain this sort of code and share it with other researchers around the Center. …


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(Pew Research Center illustration)

(Related posts: Exploring survey data with the pewmethods R package, Weighting survey data with the pewmethods R package and Analyzing international survey data with the pewmethods R package)

The Methods team at Pew Research Center is proud to release version 1.0 of pewmethods, an R package containing various functions that we use in our day-to-day survey data work. The package was originally envisioned as an internal way to reuse, maintain and share code. …


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In a recent study about online opt-in polling, Pew Research Center compared a variety of weighting approaches and found that complex statistical adjustments using machine learning don’t perform much better than raking, a simple weighting technique that pollsters have used for decades. Instead, accuracy depended much more on the choice of variables used in the adjustment. We were able to achieve greater accuracy using an expanded set of politically-related variables than we were using demographics alone.

Since then, a number of people have asked us why we didn’t include multilevel regression and poststratification (MRP) in our study. MRP is an…

Arnold Lau

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