Abstract

Discrete choice experiments are widely used in a broad area of research fields to capture the preference structure of respondents. The design of such experiments will determine to a large extent the accuracy with which the preference parameters can be estimated. This paper presents a new R package, called idefix, which enables users to generate optimal designs for discrete choice experiments. Besides Bayesian D-efficient designs for the multinomial logit model, the package includes functions to generate Bayesian adaptive designs which can be used to gather data for the mixed logit model. In addition, the package provides the necessary tools to set up actual surveys and collect empirical data. After data collection, idefix can be used to transform the data into the necessary format in order to use existing estimation software in R.

Highlights

  • Discrete choice experiments (DCE's) are used to gather stated preference data

  • This family of models is known as random utility maximization (RUM) models, and the most well known members are the multinomial logit model (MNL) (McFadden 1974), and the mixed logit model (MIXL) (Hensher and Greene 2003; McFadden and Train 2000; Train 2003)

  • The idea behind such models is that people maximize their utility, which is modeled as a function of idefix: optimal designs for DCE’s the preference weights and attribute levels

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Summary

Introduction

Discrete choice experiments (DCE's) are used to gather stated preference data. In a typical DCE, the respondent is presented several choice sets. Where orthogonal designs were mostly used at first, statistically optimal designs have acquired a prominent place in the literature on discrete choice experiments (Johnson et al 2013) The latter aims to select those choice sets that forces the respondent to make trade-offs, hereby maximizing the information gained from each observed choice, or alternatively phrased, to minimize the confidence ellipsoids around the parameter estimates. In order to reduce this sensitivity, Bayesian efficient designs were developed In the latter, the researcher acknowledges his uncertainty about the true parameters by specifying a prior preference distribution. It is limited to effects coded designs, and does not allow the user to specify alternative specific constants Such design packages are still often used, because some linearly optimized designs are optimal for MNL models when the preference parameters are assumed to be zero.

Guidelines on specifying an appropriate prior distribution
Gathering prior information
Quantifying prior information
Test prior assumptions and robustness
Summary
The multinomial logit model
Optimal designs for the MNL model
Optimal designs for the MNL model with package idefix
$`design
The mixed logit model
Optimal designs for the mixed logit model
Optimal designs for the MIXL model with package idefix
Real surveys with idefix
Online surveys
Data management
Load data
Data transformation
Future development

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