Author: Keith Goldfeld

Feed: R-bloggers. Author: Keith Goldfeld. [This article was first published on ouR data generation, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here) Want to share your content on R-bloggers? click here if you have a blog, or here if you don't. Under normal conditions, conducting a randomized clinical trial is challenging. Throw in a pandemic and things like site selection, patient recruitment and patient follow-up can be particularly vexing. In any study, subjects need to be retained long enough so that outcomes can be measured; during a period when there are so ... Read More

Feed: R-bloggers. Author: Keith Goldfeld. [This article was first published on ouR data generation, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here) Want to share your content on R-bloggers? click here if you have a blog, or here if you don't. As I mentioned last time, I am working on an update of simstudy that will make generating survival/time-to-event data a bit more flexible. I previously presented the functionality related to competing risks, and this time I’ll describe generating survival data that has time-dependent hazard ratios. (As I mentioned last time, if ... Read More

Feed: R-bloggers. Author: Keith Goldfeld. [This article was first published on ouR data generation, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here) Want to share your content on R-bloggers? click here if you have a blog, or here if you don't. I am working on an update of simstudy that will make generating survival/time-to-event data a bit more flexible. There are two biggish enhancements. The first facilitates generation of competing events, and the second allows for the possibility of generating survival data that has time-dependent hazard ratios. This post focuses on the ... Read More

Feed: R-bloggers. Author: Keith Goldfeld. [This article was first published on ouR data generation, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here) Want to share your content on R-bloggers? click here if you have a blog, or here if you don't. In the previous post I described how to determine the parameter values for generating a Weibull survival curve that reflects a desired distribution defined by two points along the curve. I went ahead and implemented these ideas in the development version of simstudy 0.4.0.9000, expanding the idea to allow for any ... Read More

Feed: R-bloggers. Author: Keith Goldfeld. The package simstudy has some functions that facilitate generating survival data using an underlying Weibull distribution. Originally, I added this to the package because I thought it would be interesting to try to do, and I figured it would be useful for me someday (and hopefully some others, as well). Well, now I am working on a project that involves evaluating at least two survival-type processes that are occurring simultaneously. To get a handle on the analytic models we might use, I’ve started to try to simulate a simplified version of the data that we ... Read More

Feed: R-bloggers. Author: Keith Goldfeld. Version 0.4.0 of simstudy is now available on CRAN and GitHub. This update includes two enhancements (and at least one major bug fix). genOrdCat now includes an argument to generate ordinal data without an assumption of cumulative proportional odds. And two new functions defRepeat and defRepeatAdd make it a bit easier to define multiple variables that share the same distribution assumptions. Ordinal data In simstudy, it is relatively easy to specify multinomial distributions that characterize categorical data. Order becomes relevant when the categories take on meanings related to strength of opinion or agreement (as in ... Read More

Feed: R-bloggers. Author: Keith Goldfeld. [This article was first published on ouR data generation, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here) Want to share your content on R-bloggers? click here if you have a blog, or here if you don't. Since this is a holiday weekend here in the US, I thought I would write up something relatively short and simple since I am supposed to be relaxing. A few weeks ago, someone presented me with some data that showed response rates to a survey that was conducted at about 30 ... Read More

Feed: R-bloggers. Author: Keith Goldfeld. [This article was first published on ouR data generation, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here) Want to share your content on R-bloggers? click here if you have a blog, or here if you don't. Over the past couple of years, I have been working with an amazing group of investigators as part of the CONTAIN trial to study whether COVID-19 convalescent plasma (CCP) can improve the clinical status of patients hospitalized with COVID-19 and requiring noninvasive supplemental oxygen. This was a multi-site study in the ... Read More

Feed: R-bloggers. Author: Keith Goldfeld. [This article was first published on ouR data generation, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here) Want to share your content on R-bloggers? click here if you have a blog, or here if you don't. Recently, a colleague submitted a paper describing the results of a Bayesian adaptive trial where the research team estimated the probability of effectiveness at various points during the trial. This trial was designed to stop as soon as the probability of effectiveness exceeded a pre-specified threshold. The journal rejected the paper ... Read More

Feed: R-bloggers. Author: Keith Goldfeld. [This article was first published on ouR data generation, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here) Want to share your content on R-bloggers? click here if you have a blog, or here if you don't. In the previous post, I described an incipient effort that I am undertaking with two colleagues, Monica Taljaard and Fan Li, to better understand the implications for collecting baseline measurements on sample size requirements for stepped wedge cluster randomized trials. (The three of us are on the Design and Statistics Core ... Read More