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Change Comes with Time: Substantive Interpretation of Nonproportional Hazards in Event History Analysis

Published online by Cambridge University Press:  04 January 2017

Amanda A. Licht
Amanda A. Licht*
Affiliation:
Department of Political Science, University of South Carolina, 3rd Floor Gambrell Hall, Columbia, SC 29205 e-mail: aalicht@gmail.com
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Abstract

Although methodologists have provided us ample notice of both the problem of nonproportional hazards (NPHs) and the means of correcting for them, less attention has been paid to the postestimation interpretation. The suggested inclusion of time interactions in our models is more than a statistical fix: These corrections alter the substantive meaning and interpretation of results. Framing the issue as a specific case of multiplicative-interaction modeling, I provide detailed discussion of the problem of NPHs and present several appropriate means of interpreting both the substantive impact and the significance of variables whose effects may change over time.

Type
Regular Articles
Information
Political Analysis , Volume 19 , Issue 2 , Spring 2011 , pp. 227 - 243
Copyright
Copyright © The Author 2011. Published by Oxford University Press on behalf of the Society for Political Methodology 

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