Kristoffer Magnusson
@rpsychologist.com
Fun fact about LMMs: when you have missing data, power also depends on the correlation between intercepts and slopes. In the clip, I’m varying the amount of random slope variance.
November 10, 2025 at 2:57 PM
Fun fact about LMMs: when you have missing data, power also depends on the correlation between intercepts and slopes. In the clip, I’m varying the amount of random slope variance.
Just added to PowerLMM.js v0.3: Interactive power contour plots!
Visualize how statistical power changes across parameter combinations.
powerlmmjs.rpsychologist.com?view=contour
Visualize how statistical power changes across parameter combinations.
powerlmmjs.rpsychologist.com?view=contour
November 7, 2025 at 4:58 PM
Just added to PowerLMM.js v0.3: Interactive power contour plots!
Visualize how statistical power changes across parameter combinations.
powerlmmjs.rpsychologist.com?view=contour
Visualize how statistical power changes across parameter combinations.
powerlmmjs.rpsychologist.com?view=contour
Wasn't that happy with how performance crashed as time points grew, so I dusted off some linear algebra to optimize the calculations. Benchmark showed a ~1Mx speedup using new implementation (with 100 time points) 😅
October 30, 2025 at 4:08 PM
Wasn't that happy with how performance crashed as time points grew, so I dusted off some linear algebra to optimize the calculations. Benchmark showed a ~1Mx speedup using new implementation (with 100 time points) 😅
October 28, 2025 at 2:02 PM
Share your analysis as a URL, or store it as a JSON file.
For example:
powerlmmjs.rpsychologist.com?n1=13&time_e...
For example:
powerlmmjs.rpsychologist.com?n1=13&time_e...
October 28, 2025 at 2:02 PM
Share your analysis as a URL, or store it as a JSON file.
For example:
powerlmmjs.rpsychologist.com?n1=13&time_e...
For example:
powerlmmjs.rpsychologist.com?n1=13&time_e...
Power analysis summary report, that can be printed or saved as a PDF
October 28, 2025 at 2:02 PM
Power analysis summary report, that can be printed or saved as a PDF
Hypothesis region visualization. Interactive display of the chosen null and alternative hypothesis.
October 28, 2025 at 2:02 PM
Hypothesis region visualization. Interactive display of the chosen null and alternative hypothesis.
New release of PowerLMM.js! Browser-based power analysis for longitudinal models with dropout.
Now includes:
- Power analysis summary report
- Reproducible & shareable configs (URL/JSON)
- Calculations validated against R
- Hypothesis region visualization
powerlmmjs.rpsychologist.com
Now includes:
- Power analysis summary report
- Reproducible & shareable configs (URL/JSON)
- Calculations validated against R
- Hypothesis region visualization
powerlmmjs.rpsychologist.com
October 28, 2025 at 2:02 PM
New release of PowerLMM.js! Browser-based power analysis for longitudinal models with dropout.
Now includes:
- Power analysis summary report
- Reproducible & shareable configs (URL/JSON)
- Calculations validated against R
- Hypothesis region visualization
powerlmmjs.rpsychologist.com
Now includes:
- Power analysis summary report
- Reproducible & shareable configs (URL/JSON)
- Calculations validated against R
- Hypothesis region visualization
powerlmmjs.rpsychologist.com
Sips is always great, I'm hosting my own sessions
June 26, 2025 at 6:53 AM
Sips is always great, I'm hosting my own sessions
Turns out proportions aren't collapsible after all. Take that, OR haters.
"Globally, approximately 3.3% of the population reports using AAS, with prevalence rates of 6.4% among men [2] and 4% among women [3]."
"Globally, approximately 3.3% of the population reports using AAS, with prevalence rates of 6.4% among men [2] and 4% among women [3]."
June 6, 2025 at 6:49 AM
Turns out proportions aren't collapsible after all. Take that, OR haters.
"Globally, approximately 3.3% of the population reports using AAS, with prevalence rates of 6.4% among men [2] and 4% among women [3]."
"Globally, approximately 3.3% of the population reports using AAS, with prevalence rates of 6.4% among men [2] and 4% among women [3]."
Not sure where to start with this one. Internet gaming addiction… is a risk factor for internet gaming disorder
May 23, 2025 at 6:29 AM
Not sure where to start with this one. Internet gaming addiction… is a risk factor for internet gaming disorder
Regarding the expert consensus on smartphone use: let’s not forget that the related “behavioral addiction” gaming disorder, is essentially a copy-paste job.
Below is a visual comparison of the ICD-11 criteria for gaming and gambling disorder—essentially a substitution of terms.
Below is a visual comparison of the ICD-11 criteria for gaming and gambling disorder—essentially a substitution of terms.
May 19, 2025 at 1:41 PM
Regarding the expert consensus on smartphone use: let’s not forget that the related “behavioral addiction” gaming disorder, is essentially a copy-paste job.
Below is a visual comparison of the ICD-11 criteria for gaming and gambling disorder—essentially a substitution of terms.
Below is a visual comparison of the ICD-11 criteria for gaming and gambling disorder—essentially a substitution of terms.
I see this a lot in longitudinal analysis—people assume missingness can depend on random effects (like slopes). But those aren’t conditioned on, so that kind of missingness would be non-ignorable (MNAR).
May 6, 2025 at 4:38 PM
I see this a lot in longitudinal analysis—people assume missingness can depend on random effects (like slopes). But those aren’t conditioned on, so that kind of missingness would be non-ignorable (MNAR).
🚨New R package! {easymediation}🚨
The *Simplest* and *Most Correct* Way to Do Causal Mediation Analysis
Are you tired of explaining mediation analysis to your colleagues? Just send them this package.
github.com/rpsychologis...
The *Simplest* and *Most Correct* Way to Do Causal Mediation Analysis
Are you tired of explaining mediation analysis to your colleagues? Just send them this package.
github.com/rpsychologis...
May 5, 2025 at 2:18 PM
🚨New R package! {easymediation}🚨
The *Simplest* and *Most Correct* Way to Do Causal Mediation Analysis
Are you tired of explaining mediation analysis to your colleagues? Just send them this package.
github.com/rpsychologis...
The *Simplest* and *Most Correct* Way to Do Causal Mediation Analysis
Are you tired of explaining mediation analysis to your colleagues? Just send them this package.
github.com/rpsychologis...
Step 1: Say data are MNAR
Step 2: Toss in random values
Step 3: Call it conservative
I’ll definitely adopt this model-free way of handling MNAR, what could go wrong?
Step 2: Toss in random values
Step 3: Call it conservative
I’ll definitely adopt this model-free way of handling MNAR, what could go wrong?
May 5, 2025 at 9:05 AM
Step 1: Say data are MNAR
Step 2: Toss in random values
Step 3: Call it conservative
I’ll definitely adopt this model-free way of handling MNAR, what could go wrong?
Step 2: Toss in random values
Step 3: Call it conservative
I’ll definitely adopt this model-free way of handling MNAR, what could go wrong?
Amazing observation in a paper: people use smartphones while waiting.
I’ve also observed that people read magazines they’d never touch anywhere else while waiting. Proposing a new disorder: "Compulsive Magazine Reading". Urgent need for intervention programs
I’ve also observed that people read magazines they’d never touch anywhere else while waiting. Proposing a new disorder: "Compulsive Magazine Reading". Urgent need for intervention programs
May 2, 2025 at 10:08 AM
Amazing observation in a paper: people use smartphones while waiting.
I’ve also observed that people read magazines they’d never touch anywhere else while waiting. Proposing a new disorder: "Compulsive Magazine Reading". Urgent need for intervention programs
I’ve also observed that people read magazines they’d never touch anywhere else while waiting. Proposing a new disorder: "Compulsive Magazine Reading". Urgent need for intervention programs
I take this to mean that none of the included studies evaluated performance with respect to the estimand of interest
April 29, 2025 at 7:02 AM
I take this to mean that none of the included studies evaluated performance with respect to the estimand of interest
Added a variogram to the app!
I'm experimenting with showing the non-stationarity of correlations in a random slopes model.
I'm experimenting with showing the non-stationarity of correlations in a random slopes model.
December 20, 2024 at 4:14 PM
Added a variogram to the app!
I'm experimenting with showing the non-stationarity of correlations in a random slopes model.
I'm experimenting with showing the non-stationarity of correlations in a random slopes model.
Added a simple illustration of group trends to demonstrate what the effect size represents
December 16, 2024 at 6:11 PM
Added a simple illustration of group trends to demonstrate what the effect size represents
Just deployed some small updates:
More tooltips!
Offloaded the most expensive computations to background threads, and added a cheeky loader for the inevitable scenario where someone tries to inverse huge matrices at 60fps+.
More tooltips!
Offloaded the most expensive computations to background threads, and added a cheeky loader for the inevitable scenario where someone tries to inverse huge matrices at 60fps+.
December 13, 2024 at 6:25 PM
Just deployed some small updates:
More tooltips!
Offloaded the most expensive computations to background threads, and added a cheeky loader for the inevitable scenario where someone tries to inverse huge matrices at 60fps+.
More tooltips!
Offloaded the most expensive computations to background threads, and added a cheeky loader for the inevitable scenario where someone tries to inverse huge matrices at 60fps+.
You can also view the implied correlation matrix and how the random slopes impact the implied standard deviations at each time point
December 11, 2024 at 10:20 AM
You can also view the implied correlation matrix and how the random slopes impact the implied standard deviations at each time point
To better understand the random effect parameters, you can view a sample of 20 random slopes adjusted to match the exact variance and correlations specified
December 11, 2024 at 10:20 AM
To better understand the random effect parameters, you can view a sample of 20 random slopes adjusted to match the exact variance and correlations specified
Dropout can be specified using either a Weibull distribution or manually
December 11, 2024 at 10:20 AM
Dropout can be specified using either a Weibull distribution or manually
Introducing PowerLMM.js!
A new tool for power analysis of longitudinal linear mixed-effects models (LMMs) – with support for missing data, plus non-inferiority and equivalence tests.
powerlmmjs.rpsychologist.com
Would really appreciate your feedback as I refine this app! Details below 🧵👇
A new tool for power analysis of longitudinal linear mixed-effects models (LMMs) – with support for missing data, plus non-inferiority and equivalence tests.
powerlmmjs.rpsychologist.com
Would really appreciate your feedback as I refine this app! Details below 🧵👇
December 11, 2024 at 10:20 AM
Introducing PowerLMM.js!
A new tool for power analysis of longitudinal linear mixed-effects models (LMMs) – with support for missing data, plus non-inferiority and equivalence tests.
powerlmmjs.rpsychologist.com
Would really appreciate your feedback as I refine this app! Details below 🧵👇
A new tool for power analysis of longitudinal linear mixed-effects models (LMMs) – with support for missing data, plus non-inferiority and equivalence tests.
powerlmmjs.rpsychologist.com
Would really appreciate your feedback as I refine this app! Details below 🧵👇