Articles by Keith Goldfeld

Generating data from a truncated distribution

August 17, 2020 | Keith Goldfeld

A researcher reached out to me the other day to see if the simstudy package provides a quick and easy way to generate data from a truncated distribution. Other than the noZeroPoisson distribution option (which is a very specific truncated distribution), there is no way to do this directly. You ...
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A hurdle model for COVID-19 infections in nursing homes

August 3, 2020 | Keith Goldfeld

Late last year, I added a mixture distribution to the simstudy package, largely motivated to accommodate zero-inflated Poisson or negative binomial distributions. (I really thought I had added this two years ago - but time is moving so slowly these days.) These distributions are useful when modeling count data, but ...
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A Bayesian model for a simulated meta-analysis

July 20, 2020 | Keith Goldfeld

This is essentially an addendum to the previous post where I simulated data from multiple RCTs to explore an analytic method to pool data across different studies. In that post, I used the nlme package to conduct a meta-analysis based on individual level data of 12 studies. Here, I am presenting ...
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Simulating multiple RCTs to simulate a meta-analysis

July 6, 2020 | Keith Goldfeld

I am currently involved with an RCT that is struggling to recruit eligible patients (by no means an unusual problem), increasing the risk that findings might be inconclusive. A possible solution to this conundrum is to find similar, ongoing trials with the aim of pooling data in a single analysis, ...
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To stratify or not? It might not actually matter…

May 11, 2020 | Keith Goldfeld

Continuing with the theme of exploring small issues that come up in trial design, I recently used simulation to assess the impact of stratifying (or not) in the context of a multi-site Covid-19 trial with a binary outcome. The investigators are concerned that baseline health status will affect the probability ...
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Can unbalanced randomization improve power?

March 30, 2020 | Keith Goldfeld

Of course, we’re all thinking about one thing these days, so it seems particularly inconsequential to be writing about anything that doesn’t contribute to solving or addressing in some meaningful way this pandemic crisis. But, I find that working provides a balm from reading and hearing all day ...
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Clustered randomized trials and the design effect

February 17, 2020 | Keith Goldfeld

I am always saying that simulation can help illuminate interesting statistical concepts or ideas. The design effect that underlies much of clustered analysis is could benefit from a little exploration through simulation. I’ve written about clustered-related methods so much on this blog that I won’t provide links - ...
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