# \#accuracy

**URL:** https://discourse.datamethods.org/tag/accuracy/9.md

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## [Discussion of A General Sample Size Framework](https://discourse.datamethods.org/t/discussion-of-a-general-sample-size-framework/28758)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 0\
**Last updated:** [May 23, 2026, 2:28pm UTC](https://discourse.datamethods.org/t/discussion-of-a-general-sample-size-framework/28758 "2026-05-23T14:28:53Z")

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This is a discussion of the 2026-04-29 paper "A general sample size framework for developing or updating a predictive algorithm: with application to clinical prediction models" by RD Riley, R Whittle, M Sadatsafavi, GP M…

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## [Lower bound for applying a concordance index (or Somers' D)](https://discourse.datamethods.org/t/lower-bound-for-applying-a-concordance-index-or-somers-d/28314)

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**Author:** [@TiborKiss](https://discourse.datamethods.org/u/TiborKiss)\
**Replies:** 3\
**Last updated:** [August 10, 2025, 11:58am UTC](https://discourse.datamethods.org/t/lower-bound-for-applying-a-concordance-index-or-somers-d/28314 "2025-08-10T11:58:54Z")

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I have a question concerning Somers’ Dxy, or C: Is there a lower bound of data points that are required to make Dxy (or C) a sensible measure? Specifically, I am investigating control items in an experimental study under…

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## [Determining the accuracy of wearable monitoring devices](https://discourse.datamethods.org/t/determining-the-accuracy-of-wearable-monitoring-devices/22595)

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**Author:** [@trumanfrancis](https://discourse.datamethods.org/u/trumanfrancis)\
**Replies:** 5\
**Last updated:** [November 13, 2024, 4:30pm UTC](https://discourse.datamethods.org/t/determining-the-accuracy-of-wearable-monitoring-devices/22595 "2024-11-13T16:30:47Z")

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Is there an accepted methodology for determining how accurate a device that measures physiologic variables like HR, HR variability, acceleration, stride length etc might be? Is it simply comparison to a “gold standard”?…

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## [Comparing prediction models without likelihoods](https://discourse.datamethods.org/t/comparing-prediction-models-without-likelihoods/4628)

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**Author:** [@noambard](https://discourse.datamethods.org/u/noambard)\
**Replies:** 8\
**Last updated:** [August 7, 2023, 1:09pm UTC](https://discourse.datamethods.org/t/comparing-prediction-models-without-likelihoods/4628 "2023-08-07T13:09:33Z")

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Hi everyone. This feels like a basic question, but we have not found a clear answer. We are studying the utility of using a novel predictor within a prediction model. The baseline and augmented models are both “xgboos…

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## [Why there isn't a popular curve for PPV vs Predicted Positives (PPCR)?](https://discourse.datamethods.org/t/why-there-isnt-a-popular-curve-for-ppv-vs-predicted-positives-ppcr/5112)

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**Author:** [@Uriah](https://discourse.datamethods.org/u/Uriah)\
**Replies:** 13\
**Last updated:** [November 22, 2022, 4:55pm UTC](https://discourse.datamethods.org/t/why-there-isnt-a-popular-curve-for-ppv-vs-predicted-positives-ppcr/5112 "2022-11-22T16:55:18Z")

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As much as I can tell there are 5 poopular curves for Performance Metrics, and the only one that includes PPV includes Sensitivity as well. In terms of prediction (and not detection) it would be more insightfull to see …

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## [Clarification on model selection example in BBR Notes](https://discourse.datamethods.org/t/clarification-on-model-selection-example-in-bbr-notes/4239)

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**Author:** [@dpananos](https://discourse.datamethods.org/u/dpananos)\
**Replies:** 3\
**Last updated:** [March 26, 2021, 1:38pm UTC](https://discourse.datamethods.org/t/clarification-on-model-selection-example-in-bbr-notes/4239 "2021-03-26T13:38:35Z")

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In section 18.4.1 of the Biostatsitics for Biomedical Research Notes, Frank Harrell offers an example of how model selection on proportion classified correctly can trick us into selecting the improper model. The example…

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## [Statistical Modeling vs. Machine Learning](https://discourse.datamethods.org/t/statistical-modeling-vs-machine-learning/5944)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 0\
**Last updated:** [September 4, 2022, 4:06pm UTC](https://discourse.datamethods.org/t/statistical-modeling-vs-machine-learning/5944 "2022-09-04T16:06:58Z")

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This is a place to discuss Roadmap for Choosing Between Statistical Modeling and Machine learning. Archive These comments and replies were made in 2018 using Disqus on a previous platform used by fharrell.com. Danilo O…

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## [Subgroups DTA meta-analysis in RevMan](https://discourse.datamethods.org/t/subgroups-dta-meta-analysis-in-revman/3066)

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**Author:** [@Danit](https://discourse.datamethods.org/u/Danit)\
**Replies:** 2\
**Last updated:** [March 9, 2020, 10:44pm UTC](https://discourse.datamethods.org/t/subgroups-dta-meta-analysis-in-revman/3066 "2020-03-09T22:44:02Z")

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Hi, I am conducting a diagnostic test accuracy on RevMan and I have different index tests for different outcomes. I am comparing each outcome for each test and then I would like to compare paired test data. However, I a…

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## [Model Performance Following Best Subset Selection](https://discourse.datamethods.org/t/model-performance-following-best-subset-selection/2921)

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**Author:** [@Lynild](https://discourse.datamethods.org/u/Lynild)\
**Replies:** 4\
**Last updated:** [January 26, 2020, 4:38pm UTC](https://discourse.datamethods.org/t/model-performance-following-best-subset-selection/2921 "2020-01-26T16:38:50Z")

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I was just curious to whether performance measures like R^2, Brier score, calibration slope/intercept etc. are as applicable on Best Subset Selection (BSS)/LASSO-based models compared to a regular GLM based model ? For …

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## [Assessing predictive accuracy in prospective studies and the effect of interventions](https://discourse.datamethods.org/t/assessing-predictive-accuracy-in-prospective-studies-and-the-effect-of-interventions/793)

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**Author:** [@beespeev](https://discourse.datamethods.org/u/beespeev)\
**Replies:** 3\
**Last updated:** [October 10, 2018, 3:12pm UTC](https://discourse.datamethods.org/t/assessing-predictive-accuracy-in-prospective-studies-and-the-effect-of-interventions/793 "2018-10-10T15:12:52Z")

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I have a question that has been an issue for me in conducting prospective analyses of risk prediction tools and accounting for the effect of intervention. Let’s say you have created an instrument (e.g. nomogram, checklis…

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## [About the accuracy category](https://discourse.datamethods.org/t/about-the-accuracy-category/44)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 0

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accuracy and information measures, discriminaton, calibration