Treatment effects beyond the mean using distributional regression: Methods and guidance

PLoS One. 2020 Feb 14;15(2):e0226514. doi: 10.1371/journal.pone.0226514. eCollection 2020.

Abstract

This paper introduces distributional regression also known as generalized additive models for location, scale and shape (GAMLSS) as a modeling framework for analyzing treatment effects beyond the mean. In contrast to mean regression models, GAMLSS relate each distributional parameter to covariates. Therefore, they can be used to model the treatment effect not only on the mean but on the whole conditional distribution. Since they encompass a wide range of different distributions, GAMLSS provide a flexible framework for modeling non-normal outcomes in which additionally nonlinear and spatial effects can easily be incorporated. We elaborate on the combination of GAMLSS with program evaluation methods including randomized controlled trials, panel data techniques, difference in differences, instrumental variables, and regression discontinuity design. We provide practical guidance on the usage of GAMLSS by reanalyzing data from the Mexican Progresa program. Contrary to expectations, no significant effects of a cash transfer on the conditional consumption inequality level between treatment and control group are found.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Data Interpretation, Statistical*
  • Databases, Factual
  • Economic Status / statistics & numerical data*
  • Humans
  • Mexico
  • Poverty / statistics & numerical data*
  • Regression Analysis
  • Statistical Distributions

Grants and funding

MH received funding from the Ministry for Science and Culture of Lower Saxony within the project “Reducing Poverty Risks in Developing Countries” and the German Research Foundation (DFG) within the research project KN 922/9-1 “Semiparametric Regression Models for Location, Scale and Shape”. PP received funding from the German Research Foundation (DFG) within the Collaborative Research Center “Ecological and Socioeconomic Functions of Tropical Lowland Rainforest Transformation Systems (Sumatra, Indonesia)”. The funders did not play any role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.