# \#interaction

**URL:** https://discourse.datamethods.org/tag/interaction/111.md

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## [Sequel to the odds ratio story](https://discourse.datamethods.org/t/sequel-to-the-odds-ratio-story/28852)

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**Author:** [@s\_doi](https://discourse.datamethods.org/u/s_doi)\
**Replies:** 14\
**Last updated:** [September 11, 2026, 12:38pm UTC](https://discourse.datamethods.org/t/sequel-to-the-odds-ratio-story/28852 "2026-09-11T12:38:32Z")

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@ngreifer posted a story here This is my sequel to that story: The patient, still frozen mid-flinch, opens one eye. “Wait. Wait wait wait. Don’t stick me yet. I think I actually understand this now.” The doctor lower…

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## [Discussion of Assessing Heterogeneity of Treatment Effect, Estimating Patient-Specific Efficacy, and Studying Variation in Odds ratios, Risk Ratios, and Risk Differences](https://discourse.datamethods.org/t/discussion-of-assessing-heterogeneity-of-treatment-effect-estimating-patient-specific-efficacy-and-studying-variation-in-odds-ratios-risk-ratios-and-risk-differences/1513)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 37\
**Last updated:** [August 23, 2026, 8:16pm UTC](https://discourse.datamethods.org/t/discussion-of-assessing-heterogeneity-of-treatment-effect-estimating-patient-specific-efficacy-and-studying-variation-in-odds-ratios-risk-ratios-and-risk-differences/1513 "2026-08-23T20:16:59Z")

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This is a place to discuss this blog article which shows an example of a formal assessment of heterogeneity of treatment effect, shows how to use penalized maximum likelihood estimation to get patient-specific efficacy e…

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## [RMS Multivariable Modeling Strategies](https://discourse.datamethods.org/t/rms-multivariable-modeling-strategies/4782)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 76\
**Last updated:** [October 28, 2025, 3:39pm UTC](https://discourse.datamethods.org/t/rms-multivariable-modeling-strategies/4782 "2025-10-28T15:39:30Z")

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Regression Modeling Strategies: Multivariable Modeling Strategies This is the fourth of several connected topics organized around chapters in Regression Modeling Strategies. The purposes of these topics are to introduce…

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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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## [Interactions and random error](https://discourse.datamethods.org/t/interactions-and-random-error/3997)

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**Author:** [@s\_doi](https://discourse.datamethods.org/u/s_doi)\
**Replies:** 24\
**Last updated:** [October 20, 2022, 9:00pm UTC](https://discourse.datamethods.org/t/interactions-and-random-error/3997 "2022-10-20T21:00:18Z")

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I have a question that leads on from observations on non-collapsible odds ratios. Let’s start with Greenlands example: This figure demonstrates the flow of stratification (X is the exposure and Y is the outcome) and c…

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## [Compare ORs between strata with log(OR) difference or use interactions?](https://discourse.datamethods.org/t/compare-ors-between-strata-with-log-or-difference-or-use-interactions/5831)

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**Author:** [@Naj](https://discourse.datamethods.org/u/Naj)\
**Replies:** 0\
**Last updated:** [July 21, 2022, 1:53pm UTC](https://discourse.datamethods.org/t/compare-ors-between-strata-with-log-or-difference-or-use-interactions/5831 "2022-07-21T13:53:57Z")

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I ran a nice model to predict mortality in a sub-cohort of patients with obesity who underwent surgery and presented that in a meeting. Upon writing the paper, the coauthors wanted to know if these predictors will predic…

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## [Relative excess risk due to interaction (RERI) from a multiplicative model](https://discourse.datamethods.org/t/relative-excess-risk-due-to-interaction-reri-from-a-multiplicative-model/5494)

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**Author:** [@eagerbo](https://discourse.datamethods.org/u/eagerbo)\
**Replies:** 3\
**Last updated:** [April 20, 2022, 11:52am UTC](https://discourse.datamethods.org/t/relative-excess-risk-due-to-interaction-reri-from-a-multiplicative-model/5494 "2022-04-20T11:52:20Z")

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Co-authors and reviewers sometimes argue, that we should calculate the RERI even though we use a multiplicative model. This is easily done in both Cox (Redirecting) and logistic models (Rothman KJ. Modern epidemiology. 1…

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## [Making sense of significant interaction with null main effect in RCT](https://discourse.datamethods.org/t/making-sense-of-significant-interaction-with-null-main-effect-in-rct/3961)

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**Author:** [@MAR](https://discourse.datamethods.org/u/MAR)\
**Replies:** 3\
**Last updated:** [December 24, 2020, 4:20pm UTC](https://discourse.datamethods.org/t/making-sense-of-significant-interaction-with-null-main-effect-in-rct/3961 "2020-12-24T16:20:05Z")

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In a clinical trial comparing two interventions for patients with a disease that has been classified into two previously well-defined subgroups, we find that the main effect of intervention B compared to intervention A o…

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## [Basic question regarding model specification for interaction testing using a Cox PH Model](https://discourse.datamethods.org/t/basic-question-regarding-model-specification-for-interaction-testing-using-a-cox-ph-model/3772)

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**Author:** [@S\_Chakraborty](https://discourse.datamethods.org/u/S_Chakraborty)\
**Replies:** 6\
**Last updated:** [September 23, 2020, 2:52pm UTC](https://discourse.datamethods.org/t/basic-question-regarding-model-specification-for-interaction-testing-using-a-cox-ph-model/3772 "2020-09-23T14:52:22Z")

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I have a very basic question regarding modelling when testing for interaction for finding heterogeneity in treatment effects in subgroups. As far as I understand the general specification of the model where a single sin…

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## [Subgroup Interaction](https://discourse.datamethods.org/t/subgroup-interaction/3183)

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**Author:** [@RenalRisk](https://discourse.datamethods.org/u/RenalRisk)\
**Replies:** 2\
**Last updated:** [April 8, 2020, 11:02pm UTC](https://discourse.datamethods.org/t/subgroup-interaction/3183 "2020-04-08T23:02:11Z")

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Long time reader, first time poster! I am a clinician trying to improve my statistical knowledge so please forgive me if this is a simplistic question. I was hoping on some guidance on assessing interactions between gro…

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## [RCT generalizability and interactions with treatment](https://discourse.datamethods.org/t/rct-generalizability-and-interactions-with-treatment/3072)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 8\
**Last updated:** [March 10, 2020, 2:35pm UTC](https://discourse.datamethods.org/t/rct-generalizability-and-interactions-with-treatment/3072 "2020-03-10T14:35:02Z")

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This topic is for discussions and questions surrounding the blog article Implications of Interactions in Treatment Comparisons. One of the themes of the article is that randomized clinical trial results can generalize q…

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## [Bayesian Modeling of Patient-Specific Efficacy Estimates and HTE](https://discourse.datamethods.org/t/bayesian-modeling-of-patient-specific-efficacy-estimates-and-hte/1793)

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**Author:** [@BenYAndrew](https://discourse.datamethods.org/u/BenYAndrew)\
**Replies:** 2\
**Last updated:** [July 2, 2019, 11:45pm UTC](https://discourse.datamethods.org/t/bayesian-modeling-of-patient-specific-efficacy-estimates-and-hte/1793 "2019-07-02T23:45:19Z")

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I have been working (along with @DanLane911) on a partial Bayesian adaptation and extension of @f2harrell’s blog post (https://www.fharrell.com/post/varyor/) examining the process of modeling HTE and the production of pa…

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## [How to display and tabulate interaction effects in a longitudinal model](https://discourse.datamethods.org/t/how-to-display-and-tabulate-interaction-effects-in-a-longitudinal-model/1106)

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**Author:** [@rm60553](https://discourse.datamethods.org/u/rm60553)\
**Replies:** 1\
**Last updated:** [December 14, 2018, 1:04pm UTC](https://discourse.datamethods.org/t/how-to-display-and-tabulate-interaction-effects-in-a-longitudinal-model/1106 "2018-12-14T13:04:19Z")

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New poster here. I did not see this topic in the list of topics going back several months. If there is an old topic covering this, point this out to me. A stat colleague of mine and I are working with clinical resear…