I’ve been participating in the design of a new study that will evaluate interventions aimed at reducing both pain and opioid use for patients on dialysis. This study is likely to be somewhat complicated, involving multiple clusters, three interventions, a sequential and adaptive randomization scheme, and a composite binary ...

I am contemplating adding a new distribution option to the package simstudy that would allow users to define a new variable as a mixture of previously defined (or already generated) variables. I think the easiest way to explain how to apply the new mixture option is to step through a ...

I am involved with a very interesting project - the NIA IMPACT Collaboratory - where a primary goal is to fund a large group of pragmatic pilot studies to investigate promising interventions to improve health care and quality of life for people living with Alzheimer’s disease and related dementias. ...

A couple of months ago, I was contacted about the possibility of creating a simple function in simstudy to generate a large dataset that could include possibly 10’s or 100’s of potential predictors and an outcome. In this function, only a subset of the variables would actually be predictors. The ...

I am collaborating with a number of folks who think a lot about palliative or supportive care for people who are facing end-stage disease, such as advanced dementia, cancer, COPD, or congestive heart failure. A major concern for this population (which really includes just about everyone at some point) is ...

“I am working on a simulation study that requires me to generate data for individuals within clusters, but each individual will have repeated measures (say baseline and two follow-ups). I’m new to simstudy and have been going through the examples in R this afternoon, but I wondered if this ...

In a current multi-site study, we are using a stepped-wedge design to evaluate whether improved training and protocols can reduce prescriptions of anti-psychotic medication for home hospice care patients with advanced dementia. The study is officially called the Hospice Advanced Dementia Symptom Management and Quality of Life (HAS-QOL) Stepped Wedge ...

A key motivating factor for the simstudy package and much of this blog is that simulation can be super helpful in understanding how best to approach an unusual, or least unfamiliar, analytic problem. About six months ago, I described the DREAM Initiative (Diabetes Research, Education, and Action for Minorities), a ...

I’m developing study simulations that require me to generate a sequence of health status for a collection of individuals. In these simulations, individuals gradually grow sicker over time, though sometimes they recover slightly. To facilitate this, I...

Continuing a series of posts discussing the structure of intra-cluster correlations (ICC’s) in the context of a stepped-wedge trial, this latest edition is primarily interested in fitting Bayesian hierarchical models for more complex cases (though I do talk a bit more about the linear mixed effects models). The first ...

In the last two posts, I introduced the notion of time-varying intra-cluster correlations in the context of stepped-wedge study designs. (See here and here). Though I generated lots of data for those posts, I didn’t fit any models to see if I could recover the estimates and any underlying ...

In my last post, I wrote about within- and between-period intra-cluster correlations in the context of stepped-wedge cluster randomized study designs. These are quite important to understand when figuring out sample size requirements (and models for analysis, which I’ll be writing about soon.) Here, I’m extending the constant ...

A few weeks ago, I was at the annual meeting of the NIH Collaboratory, which is an innovative collection of collaboratory cores, demonstration projects, and NIH Institutes and Centers that is developing new models for implementing and supporting large-scale health services research. A study I am involved with - Primary ...

It is always exciting to find an interesting pattern in the data that seems to point to some important difference or relationship. A while ago, one of my colleagues shared a figure with me that looked something like this: It looks like something is going on. On average low scorers ...

simstudy has just been updated (version 0.1.13 on CRAN), and includes one interesting addition (and a couple of bug fixes). I am working on a post (or two) about intra-cluster correlations (ICCs) and stepped-wedge study designs (which I’ve written about before), and I was getting tired of going through the ...

A couple of weeks ago, I was inspired by a study to write about a classic design issue that arises in cluster randomized trials: should we focus on the number of clusters or the size of those clusters? This trial, which is concerned with preventing opioid use disorder for at-risk ...

I am involved with a trial of an intervention designed to prevent full-blown opioid use disorder for patients who may have an incipient opioid use problem. Given the nature of the intervention, it was clear the only feasible way to conduct this particular study is to randomize at the physician ...

Randomization is super useful because it usually eliminates the risk that confounding will lead to a biased estimate of a treatment effect. However, this only goes so far. If you are conducting a meditation analysis in the hopes of understanding the underlying causal mechanism of a treatment, it is important ...

I’ve been meaning to share an analysis I recently did to estimate the strength of the relationship between a young child’s ability to recognize emotions in others (e.g. teachers and fellow students) and her longer term academic success. The study itself is quite interesting (hopefully it will ...

Analysis is important, but study design is paramount. I am involved with the Diabetes Research, Education, and Action for Minorities (DREAM) Initiative, which is, among other things, estimating the effect of a group-based therapy program on weight loss for patients who have been identified as pre-diabetic (which means they have ...