Search Results for author: Chirag Nagpal

Found 15 papers, 5 papers with code

Deep Cox Mixtures for Survival Regression

4 code implementations16 Jan 2021 Chirag Nagpal, Steve Yadlowsky, Negar Rostamzadeh, Katherine Heller

Survival analysis is a challenging variation of regression modeling because of the presence of censoring, where the outcome measurement is only partially known, due to, for example, loss to follow up.

regression Survival Analysis

Counterfactual Phenotyping with Censored Time-to-Events

2 code implementations22 Feb 2022 Chirag Nagpal, Mononito Goswami, Keith Dufendach, Artur Dubrawski

Estimation of treatment efficacy of real-world clinical interventions involves working with continuous outcomes such as time-to-death, re-hospitalization, or a composite event that may be subject to censoring.

counterfactual Counterfactual Reasoning

auton-survival: an Open-Source Package for Regression, Counterfactual Estimation, Evaluation and Phenotyping with Censored Time-to-Event Data

2 code implementations15 Apr 2022 Chirag Nagpal, Willa Potosnak, Artur Dubrawski

Applications of machine learning in healthcare often require working with time-to-event prediction tasks including prognostication of an adverse event, re-hospitalization or death.

BIG-bench Machine Learning counterfactual +1

Nonlinear Semi-Parametric Models for Survival Analysis

1 code implementation14 May 2019 Chirag Nagpal, Rohan Sangave, Amit Chahar, Parth Shah, Artur Dubrawski, Bhiksha Raj

Semi-parametric survival analysis methods like the Cox Proportional Hazards (CPH) regression (Cox, 1972) are a popular approach for survival analysis.

regression Survival Analysis

Preserving Intermediate Objectives: One Simple Trick to Improve Learning for Hierarchical Models

no code implementations23 Jun 2017 Abhilasha Ravichander, Shruti Rijhwani, Rajat Kulshreshtha, Chirag Nagpal, Tadas Baltrušaitis, Louis-Philippe Morency

In this work, we focus on improving learning for such hierarchical models and demonstrate our method on the task of speaker trait prediction.

Persuasiveness

Bayesian Consensus: Consensus Estimates from Miscalibrated Instruments under Heteroscedastic Noise

no code implementations14 Apr 2020 Chirag Nagpal, Robert E. Tillman, Prashant Reddy, Manuela Veloso

We consider the problem of aggregating predictions or measurements from a set of human forecasters, models, sensors or other instruments which may be subject to bias or miscalibration and random heteroscedastic noise.

Bayesian Inference

Recovering Sparse and Interpretable Subgroups with Heterogeneous Treatment Effects with Censored Time-to-Event Outcomes

no code implementations24 Feb 2023 Chirag Nagpal, Vedant Sanil, Artur Dubrawski

In this paper we propose a statistical approach to recovering sparse phenogroups (or subtypes) that demonstrate differential treatment effects as compared to the study population.

Helping or Herding? Reward Model Ensembles Mitigate but do not Eliminate Reward Hacking

no code implementations14 Dec 2023 Jacob Eisenstein, Chirag Nagpal, Alekh Agarwal, Ahmad Beirami, Alex D'Amour, DJ Dvijotham, Adam Fisch, Katherine Heller, Stephen Pfohl, Deepak Ramachandran, Peter Shaw, Jonathan Berant

However, even pretrain reward ensembles do not eliminate reward hacking: we show several qualitative reward hacking phenomena that are not mitigated by ensembling because all reward models in the ensemble exhibit similar error patterns.

Language Modelling

Theoretical guarantees on the best-of-n alignment policy

no code implementations3 Jan 2024 Ahmad Beirami, Alekh Agarwal, Jonathan Berant, Alexander D'Amour, Jacob Eisenstein, Chirag Nagpal, Ananda Theertha Suresh

A commonly used analytical expression in the literature claims that the KL divergence between the best-of-$n$ policy and the base policy is equal to $\log (n) - (n-1)/n.$ We disprove the validity of this claim, and show that it is an upper bound on the actual KL divergence.

Transforming and Combining Rewards for Aligning Large Language Models

no code implementations1 Feb 2024 ZiHao Wang, Chirag Nagpal, Jonathan Berant, Jacob Eisenstein, Alex D'Amour, Sanmi Koyejo, Victor Veitch

A common approach for aligning language models to human preferences is to first learn a reward model from preference data, and then use this reward model to update the language model.

Language Modelling

Bias in Language Models: Beyond Trick Tests and Toward RUTEd Evaluation

no code implementations20 Feb 2024 Kristian Lum, Jacy Reese Anthis, Chirag Nagpal, Alexander D'Amour

In this work, we study the correspondence between such decontextualized "trick tests" and evaluations that are more grounded in Realistic Use and Tangible {Effects (i. e. RUTEd evaluations).

Text Generation

The Case for Globalizing Fairness: A Mixed Methods Study on Colonialism, AI, and Health in Africa

no code implementations5 Mar 2024 Mercy Asiedu, Awa Dieng, Iskandar Haykel, Negar Rostamzadeh, Stephen Pfohl, Chirag Nagpal, Maria Nagawa, Abigail Oppong, Sanmi Koyejo, Katherine Heller

Whereas experts generally expressed a shared view about the relevance of colonial history for the development and implementation of AI technologies in Africa, the majority of the general population participants surveyed did not think there was a direct link between AI and colonialism.

Attribute Fairness

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