Articles by Keith Goldfeld

Considering sensitivity to unmeasured confounding: part 1

January 1, 2019 | Keith Goldfeld

Principled causal inference methods can be used to compare the effects of different exposures or treatments we have observed in non-experimental settings. These methods, which include matching (with or without propensity scores), inverse probability weighting, and various g-methods, help us create comparable groups to simulate a randomized experiment. All of ...
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Horses for courses, or to each model its own (causal effect)

November 27, 2018 | Keith Goldfeld

In my previous post, I described a (relatively) simple way to simulate observational data in order to compare different methods to estimate the causal effect of some exposure or treatment on an outcome. The underlying data generating process (DGP) included a possibly unmeasured confounder and an instrumental variable. (If you ...
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Causal mediation estimation measures the unobservable

November 5, 2018 | Keith Goldfeld

I put together a series of demos for a group of epidemiology students who are studying causal mediation analysis. Since mediation analysis is not always so clear or intuitive, I thought, of course, that going through some examples of simulating data for this process could clarify things a bit. Quite ...
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Cross-over study design with a major constraint

October 22, 2018 | Keith Goldfeld

Every new study presents its own challenges. (I would have to say that one of the great things about being a biostatistician is the immense variety of research questions that I get to wrestle with.) Recently, I was approached by a group of researchers who wanted to evaluate an intervention. ...
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simstudy update: improved correlated binary outcomes

September 24, 2018 | Keith Goldfeld

An updated version of the simstudy package (0.1.10) is now available on CRAN. The impetus for this release was a series of requests about generating correlated binary outcomes. In the last post, I described a beta-binomial data generating process that uses the recently added beta distribution. In addition to that update, ...
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Binary, beta, beta-binomial

September 10, 2018 | Keith Goldfeld

I’ve been working on updates for the simstudy package. In the past few weeks, a couple of folks independently reached out to me about generating correlated binary data. One user was not impressed by the copula algorithm that is already implemented. I’ve added an option to use an ...
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The power of stepped-wedge designs

August 27, 2018 | Keith Goldfeld

Just before heading out on vacation last month, I put up a post that purported to compare stepped-wedge study designs with more traditional cluster randomized trials. Either because I rushed or was just lazy, I didn’t exactly do what I set out to do. I did confirm that a ...
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Multivariate ordinal categorical data generation

August 14, 2018 | Keith Goldfeld

An economist contacted me about the ability of simstudy to generate correlated ordinal categorical outcomes. He is trying to generate data as an aide to teaching cost-effectiveness analysis, and is hoping to simulate responses to a quality-of-life survey instrument, the EQ-5D. The particular instrument has five questions related to ...
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Randomize by, or within, cluster?

July 18, 2018 | Keith Goldfeld

I am involved with a stepped-wedge designed study that is exploring whether we can improve care for patients with end-stage disease who show up in the emergency room. The plan is to train nurses and physicians in palliative care. (A while ago, I described what the stepped wedge design is.) ...
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