Archive ScienceWatch



David P. MacKinnon talks with and answers a few questions about this month's Fast Moving Front in the field of Economics & Business.
MacKinnon Article: A comparison of methods to test mediation and other intervening variable effects
Authors: MacKinnon, DP;Lockwood, CM;Hoffman, JM;West, SG;Sheets, V
Journal: PSYCHOL METHODS, 7 (1): 83-104 MAR 2002
Addresses: Arizona State Univ, Dept Psychol, Tempe, AZ 85287 USA.
Arizona State Univ, Dept Psychol, Tempe, AZ 85287 USA.

Why do you think your paper is highly cited?

The paper investigates an important method in many fields, the extent to which a variable transmits or mediates the relation between an independent and a dependent variable. The paper reviews existing tests for mediating variables from many different fields and describes several new tests.

One reason why the paper is highly cited is that it has a broad perspective to include tests from many different areas of inquiry. In some cases, widely used methods did not perform as well as expected in statistical simulations. Information on the different tests and their statistical performance had not appeared in the research literature before.

Does it describe a new discovery, methodology, or synthesis of knowledge?

There are several new tests in the article. A large number of different methodologies had been used to investigate mediating variables and this article was the first to compare them theoretically and with a statistical simulation.

Would you summarize the significance of your paper in layman's terms?

Mediation analysis is useful in many areas. One modern use of this method is to determine how treatment and prevention programs achieve their effects. For example, mediation analysis can be used to assess whether a program reduced cigarette smoking by increased social support for quitting tobacco use.

Mediation analysis can be used to investigate how a program to reduce heart attacks achieves its effects, such as whether the program reduced blood pressure which then reduced subsequent heart attacks. If researchers know how a treatment or prevention program works then more efficient and less expensive treatment and prevention programs can be developed.

How did you become involved in this research and were there any particular problems encountered along the way?

I became involved in this research around 1987 when I was asked to investigate how a school-based drug prevention program achieved its effects. In the course of this research, I realized that there were many different tests of mediation from many different fields. It was unclear which test or tests were the best to use. As I learned more about these tests, I learned that they differed widely in their statistical performance. Importantly, this research received support from the National Institute on Drug Abuse.

Where do you see your research leading in the future?

The paper describes a relatively simple mediation model. Future work is now addressing mediation analysis when variables are categorical, when longitudinal data are collected, influence of violation of assumptions, and experimental designs to assess mediation.

Do you foresee any social or political implications for your research?

Mediation analysis has the capability of improving treatment and prevention programs. Mediation analysis can also improve existing social programs so that they may have greater effects and even cost less.

David P. MacKinnon, Ph.D.
Foundation Professor of Psychology
Arizona State University
Tempe, AZ, USA

Keywords: mediating variables, statistical simulations, mediation analysis.


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