Page 37 - The Importance of Common Metrics for Advacing Social Science Theory and Research

The Importance of Common Metrics for Advancing Social Science Theory and Research: A Workshop Summary
http://www.nap.edu/catalog/13034.html

MEASUREMENT IN THE SOCIAL SCIENCES 25

• U.S. aversion to using weights from other countries.
• Lack of interest from NIH institutes that are generally disease- or
organ-focused and seek measures sensitive to their issues, with the
National Institute on Aging being the exception.

Patient-Reported Outcomes Measurement Information System
PROMIS is part of the NIH Roadmap using IRT to scale the different
domains of health. Each dimension has its own item bank and scale, which
can be improved over time. Fryback described the conceptual framework
for health in PROMIS as similar to HRQoL, but the measurement basis is
very different. In PROMIS, IRT is used to create a separate psychometric
scale for each dimension; there is no combining of scales into a single sum-
mary. He reported that PROMIS has developed an Internet-based interface
using computer-adaptive testing to minimize response burden. Item banks
are now available for only a few of the health dimensions; once there are
item banks for all of the dimensions, PROMIS can use psychometric tech-
niques, including IRT, to scale health items, and it can be improved over
time as questions are added and improved and not necessarily affixed to
one questionnaire. The final step, said Fryback, is to implement a scoring
function to complete the HRQoL index. He believes there are many reasons
to implement standard measures of HRQoL and that PROMIS offers a path
for the future.

DISCUSSION

In his remarks, Jack Triplett (Brookings Institution) discussed the role
of theory in economic measurement, but balanced it with a discussion of the
limitations of economic theory as a guide to economic measurement. On the
measurement of medical care in economics, he tied Fryback’s presentation
on medical outcomes measures to problems in the economic measurement
of medical care prices and output to show how some measurement prob-
lems in economics require information from outside economics.
To illustrate the usefulness of economic theory, he offered three ex-
amples of cases in which construction of economic data is guided by eco-
nomic theory:

• Gross domestic product: The basic structure of GDP is given in
the equation Y = C + I + G, where Y is income generated, C is
consumption expenditures, I is investment expenditures, and G is
government expenditure. This equation is a fundamental analytical
equation that comes right out of macroeconomic theory developed
by Maynard Keynes more than 70 years ago. The basic structure of

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