# \#model-specification

**URL:** https://discourse.datamethods.org/tag/model-specification/93.md

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## [Censored binomial models](https://discourse.datamethods.org/t/censored-binomial-models/28732)

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**Author:** [@Ahmed\_Sayed](https://discourse.datamethods.org/u/Ahmed_Sayed)\
**Replies:** 6\
**Last updated:** [May 17, 2026, 12:48pm UTC](https://discourse.datamethods.org/t/censored-binomial-models/28732 "2026-05-17T12:48:20Z")

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Hi all, Suppose I have the following problem: I have 100 surgeons, each of whom perform N{i} procedures in a given year to treat a particular condition. For our particular condition, they have the option of performing…

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## [Best model reduction approach for Fine-Gray prediction model](https://discourse.datamethods.org/t/best-model-reduction-approach-for-fine-gray-prediction-model/28678)

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**Author:** [@rafdoodle1](https://discourse.datamethods.org/u/rafdoodle1)\
**Replies:** 5\
**Last updated:** [March 27, 2026, 11:27am UTC](https://discourse.datamethods.org/t/best-model-reduction-approach-for-fine-gray-prediction-model/28678 "2026-03-27T11:27:38Z")

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Hello there, I am developing a Fine-Gray competing risks prediction model for dementia incidence (with death as the competing event) using population-based survey data linked to administrative health records. My full mo…

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## [RMS General Regression](https://discourse.datamethods.org/t/rms-general-regression/4705)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 121\
**Last updated:** [May 22, 2025, 6:23pm UTC](https://discourse.datamethods.org/t/rms-general-regression/4705 "2025-05-22T18:23:02Z")

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Regression Modeling Strategies: General Aspects of Fitting Regression Models This is the second of several connected topics organized around chapters in Regression Modeling Strategies. The purposes of these topics are t…

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## [Using 2 different measures of the same entity for risk prediction](https://discourse.datamethods.org/t/using-2-different-measures-of-the-same-entity-for-risk-prediction/22365)

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**Author:** [@Ahmed\_Sayed](https://discourse.datamethods.org/u/Ahmed_Sayed)\
**Replies:** 3\
**Last updated:** [November 12, 2024, 12:41pm UTC](https://discourse.datamethods.org/t/using-2-different-measures-of-the-same-entity-for-risk-prediction/22365 "2024-11-12T12:41:41Z")

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Hello everyone, I am currently analyzing a dataset where measurements of the same entity (coronary blood flow) are taken in 2 states (with negligible temporal separation between the 2 measurements). The first is the “re…

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## [What do you think of the state of surrogate endpoint validation in chronic kidney disease?](https://discourse.datamethods.org/t/what-do-you-think-of-the-state-of-surrogate-endpoint-validation-in-chronic-kidney-disease/17977)

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**Author:** [@mnarayan](https://discourse.datamethods.org/u/mnarayan)\
**Replies:** 6\
**Last updated:** [July 31, 2024, 3:39pm UTC](https://discourse.datamethods.org/t/what-do-you-think-of-the-state-of-surrogate-endpoint-validation-in-chronic-kidney-disease/17977 "2024-07-31T15:39:52Z")

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I’ve seen a number of papers now including this recent Nature Medicine paper purporting to validate candidate surrogate endpoints for chronic kidney disease (CKD). All things considered, it seems like a sound meta-analy…

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## [AIC vs qq-plot for deciding the best model](https://discourse.datamethods.org/t/aic-vs-qq-plot-for-deciding-the-best-model/7472)

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**Author:** [@kiwiskiNZ](https://discourse.datamethods.org/u/kiwiskiNZ)\
**Replies:** 2\
**Last updated:** [February 11, 2024, 7:59pm UTC](https://discourse.datamethods.org/t/aic-vs-qq-plot-for-deciding-the-best-model/7472 "2024-02-11T19:59:36Z")

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I’ve been playing with some simulated data in preparation for analysis of a stepped wedge randomised control trial. I will be using a mixed model (and the lmer() function in R). The response variable is length of stay …

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## [RMS Introduction](https://discourse.datamethods.org/t/rms-introduction/4465)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 7\
**Last updated:** [May 22, 2023, 3:48am UTC](https://discourse.datamethods.org/t/rms-introduction/4465 "2023-05-22T03:48:02Z")

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Regression Modeling Strategies: Introduction This is the first of several connected topics organized around chapters in Regression Modeling Strategies. The purposes of these topics are to introduce key concepts in the c…

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## [How to handle multiple tests per patient in the development of diagnostic prediction model?](https://discourse.datamethods.org/t/how-to-handle-multiple-tests-per-patient-in-the-development-of-diagnostic-prediction-model/7002)

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**Author:** [@arthur\_albuquerque](https://discourse.datamethods.org/u/arthur_albuquerque)\
**Replies:** 2\
**Last updated:** [August 15, 2023, 11:11am UTC](https://discourse.datamethods.org/t/how-to-handle-multiple-tests-per-patient-in-the-development-of-diagnostic-prediction-model/7002 "2023-08-15T11:11:14Z")

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I am planning to develop and internally validate a diagnostic prediction model from a retrospective cohort database. I will follow a cross-sectional study design, hence I’ll apply a logistic regression model. My populati…

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## [When do we adjust for baseline characteristics?](https://discourse.datamethods.org/t/when-do-we-adjust-for-baseline-characteristics/6270)

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**Author:** [@Hanis\_Kadir](https://discourse.datamethods.org/u/Hanis_Kadir)\
**Replies:** 3\
**Last updated:** [December 23, 2022, 12:30am UTC](https://discourse.datamethods.org/t/when-do-we-adjust-for-baseline-characteristics/6270 "2022-12-23T00:30:57Z")

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Hi all, If we are doing a regression model, descriptive type; trying to assess multiple factors of interest with the outcome, do we need to adjust for baseline characteristics (regardless of significance)? I understand…

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## [Treating data points that belong to several categories in regressions](https://discourse.datamethods.org/t/treating-data-points-that-belong-to-several-categories-in-regressions/5053)

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**Author:** [@Tomer\_Milo](https://discourse.datamethods.org/u/Tomer_Milo)\
**Replies:** 1\
**Last updated:** [November 3, 2021, 12:08pm UTC](https://discourse.datamethods.org/t/treating-data-points-that-belong-to-several-categories-in-regressions/5053 "2021-11-03T12:08:23Z")

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Assume a simple linear regression model with varying intercepts and slopes: I have a dataset with one continuous predictor (x) and one categorial predictor (“category”). Let’s say 2 categories. I want to infer a1, a2,…

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## [Beta-binomial distributions using BRMS in R - How should I use the custom\_family argument?](https://discourse.datamethods.org/t/beta-binomial-distributions-using-brms-in-r-how-should-i-use-the-custom-family-argument/3906)

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**Author:** [@IdaC](https://discourse.datamethods.org/u/IdaC)\
**Replies:** 0\
**Last updated:** [November 11, 2020, 10:58am UTC](https://discourse.datamethods.org/t/beta-binomial-distributions-using-brms-in-r-how-should-i-use-the-custom-family-argument/3906 "2020-11-11T10:58:07Z")

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I’m trying to compute a beta-binomial model using the R package brms. However, beta-binomial distributions are not native to this package, so I’m trying to use the custom\_family argument, to create the family myself. I’v…

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## [Bayesian Solutions for Challenges to Frequentist Statistics](https://discourse.datamethods.org/t/bayesian-solutions-for-challenges-to-frequentist-statistics/3764)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 0\
**Last updated:** [September 22, 2020, 1:08pm UTC](https://discourse.datamethods.org/t/bayesian-solutions-for-challenges-to-frequentist-statistics/3764 "2020-09-22T13:08:25Z")

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Ability to Use External Information A skeptical prior distribution may be used when it is known that a therapy is incremental and not curative. In the less common situation where one has excellent data about the same tr…

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## [Choice of variables to include in regression model specification and risk of bias assessments](https://discourse.datamethods.org/t/choice-of-variables-to-include-in-regression-model-specification-and-risk-of-bias-assessments/3706)

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**Author:** [@Shillcutt](https://discourse.datamethods.org/u/Shillcutt)\
**Replies:** 0\
**Last updated:** [August 27, 2020, 10:14pm UTC](https://discourse.datamethods.org/t/choice-of-variables-to-include-in-regression-model-specification-and-risk-of-bias-assessments/3706 "2020-08-27T22:14:14Z")

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The objective of this (revised) blog is to ask three questions: What published studies provide exemplary rationale to support choices of variables for a conceptual framework to support regression analysis? Given defini…

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## [Another point against automatic selection?](https://discourse.datamethods.org/t/another-point-against-automatic-selection/3663)

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**Author:** [@Shillcutt](https://discourse.datamethods.org/u/Shillcutt)\
**Replies:** 0\
**Last updated:** [August 21, 2020, 5:34pm UTC](https://discourse.datamethods.org/t/another-point-against-automatic-selection/3663 "2020-08-21T17:34:34Z")

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This blog describes a potential point to add to the case against automatic selection \[1,2\]. Please consider two bottom line questions up front. Do any other empirical examples exist of automatic selection not being tra…

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## [Post-Hoc Assumption Tests](https://discourse.datamethods.org/t/post-hoc-assumption-tests/3318)

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**Author:** [@albertoca](https://discourse.datamethods.org/u/albertoca)\
**Replies:** 1\
**Last updated:** [May 13, 2020, 1:26am UTC](https://discourse.datamethods.org/t/post-hoc-assumption-tests/3318 "2020-05-13T01:26:35Z")

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In Datamethods, model assumptions are often discussed, and what to do when they are not met. It has already been explained on several occasions that rational alternatives include using methods that relax the most common …

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## [Validity of comparing specific predictors from two non-nested models](https://discourse.datamethods.org/t/validity-of-comparing-specific-predictors-from-two-non-nested-models/3228)

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**Author:** [@mkvdp](https://discourse.datamethods.org/u/mkvdp)\
**Replies:** 4\
**Last updated:** [April 24, 2020, 11:31pm UTC](https://discourse.datamethods.org/t/validity-of-comparing-specific-predictors-from-two-non-nested-models/3228 "2020-04-24T23:31:44Z")

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I’m working with a dataset comprising various physiological measurements (as well as some relevant demographic variables) of the femur in 289 participants. Multiple variables are indices for which I have both CT- and MRI…

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## [Model selection process](https://discourse.datamethods.org/t/model-selection-process/3076)

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**Author:** [@romain](https://discourse.datamethods.org/u/romain)\
**Replies:** 1\
**Last updated:** [March 5, 2020, 8:16pm UTC](https://discourse.datamethods.org/t/model-selection-process/3076 "2020-03-05T20:16:06Z")

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I have about 30 variables that I think might be useful for modelling my outcome which is a binary variable. Before I select my model I want to preregister. What is the standard way to do this? For example, when selecti…

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## [Many Analysts, One Data Set – many conclusions](https://discourse.datamethods.org/t/many-analysts-one-data-set-many-conclusions/1051)

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**Author:** [@RonanConroy](https://discourse.datamethods.org/u/RonanConroy)\
**Replies:** 11\
**Last updated:** [December 12, 2018, 9:47pm UTC](https://discourse.datamethods.org/t/many-analysts-one-data-set-many-conclusions/1051 "2018-12-12T21:47:08Z")

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Medscape psychiatry has a good write-up of a very interesting paper by Silberzahn and colleagues in which they got 29 teams, involving 61 analysts, who used the same data set to address the same research question: whethe…

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## [Nosek et al paper](https://discourse.datamethods.org/t/nosek-et-al-paper/819)

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**Author:** [@drjohnm](https://discourse.datamethods.org/u/drjohnm)\
**Replies:** 18\
**Last updated:** [October 19, 2018, 12:46pm UTC](https://discourse.datamethods.org/t/nosek-et-al-paper/819 "2018-10-19T12:46:22Z")

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Would love to get the opinion of experts on the Nosek et al paper showing that 29 research groups analyzed the same data on same research question and found disparate odds ratios depending on analysis type. http://journ…