Project Summary

One of PCORI’s goals is to improve the methods that researchers use for patient-centered outcomes research. PCORI funds methods projects like this one to better understand and advance the use of research methods that improve the strength and quality of comparative effectiveness research.

This research project is in progress. PCORI will post the research findings on this page within 90 days after the results are final.

What is the project about?

In observational studies, researchers look at what happens after patients and their doctors choose treatments. In these studies, patients with different traits—for example, older or younger patients—may choose different treatments. As a result, researchers may have a hard time knowing if it was the treatment that affected patient health outcomes, or whether patient traits affected the outcomes. Statistical methods can help address this problem.

Propensity score, or PS, methods can help researchers conduct observational studies. When looking at outcomes for different treatments, researchers can use PS methods to balance treatment groups. That is, they can account for differences in traits among patients who get different treatments and improve understanding of whether effects are due to the treatment or patients’ traits. But by creating more balanced, and often smaller, treatment groups, PS methods can decrease precision, making results less certain.

Subgroup analyses show how the same treatment affects groups of patients differently. For example, a treatment might work better for younger patients than older ones. PS methods can be used to study subgroups, but standard PS methods may not work well in subgroups.   

In this study, the research team is developing new methods for testing balance and precision when planning subgroup analyses. The team is also developing new PS methods for conducting subgroup analyses.

How can this project help improve research methods?

Results may help researchers get information about what treatments work best for different groups of patients that is more accurate and precise.

What is the research team doing?

First, the research team is developing methods researchers can use to assess balance and precision when designing subgroup analyses. The methods detect and solve potential problems that could arise in subgroup analyses. Second, the team is developing new PS methods that use machine learning to improve balance and precision. In machine learning, computers use data to learn how to perform different tasks with little or no human input. Third, the team is comparing the new methods to existing methods to determine which methods are best for conducting subgroup analyses. Finally, the team is testing the new methods using data on treatments for women with uterine fibroids.  

Research methods at a glance

Design Elements Description
  • To develop new ways for researchers to test balance and precision when planning subgroup analyses for observational studies
  • To develop new PS methods for conducting subgroup analyses

Simulation, machine learning, propensity scoring, subgroup analyses

Project Information

Laine E. Thomas, PhD
Duke University
Methods for the Design and Conduct of Subgroup Analysis in Observational Studies

Key Dates

April 2019
September 2023

Study Registration Information


Has Results
Award Type
Health Conditions Health Conditions These are the broad terms we use to categorize our funded research studies; specific diseases or conditions are included within the appropriate larger category. Note: not all of our funded projects focus on a single disease or condition; some touch on multiple diseases or conditions, research methods, or broader health system interventions. Such projects won’t be listed by a primary disease/condition and so won’t appear if you use this filter tool to find them. View Glossary
Intervention Strategy Intervention Strategies PCORI funds comparative clinical effectiveness research (CER) studies that compare two or more options or approaches to health care, or that compare different ways of delivering or receiving care. View Glossary
State State The state where the project originates, or where the primary institution or organization is located. View Glossary
Last updated: October 25, 2023