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Related Experiment Videos

Fitting wald and ex-Wald distributions to response time data: an example using functions for the S-PLUS package.

Andrew Heathcote1

  • 1School of Behavioural Sciences, University of Newcastle, Callaghan 2308, NSW, Australia. andrew.healthcote@newcastle.edu.au

Behavior Research Methods, Instruments, & Computers : a Journal of the Psychonomic Society, Inc
|January 12, 2005
PubMed
Summary

Adequate parameter estimation for the ex-Wald distribution requires at least 400 samples. The shifted Wald distribution, however, needs fewer samples for accurate estimation, especially when excluding ill-conditioned fits.

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Area of Science:

  • Psychology
  • Statistics
  • Computational Science

Background:

  • The ex-Wald distribution models simple and go/no-go response times.
  • Accurate parameter estimation is crucial for the validity of these response time models.

Purpose of the Study:

  • To provide S-PLUS functions for estimating parameters of the ex-Wald, shifted Wald, and ex-Gaussian distributions.
  • To evaluate the efficiency and bias of parameter estimates through a Monte Carlo simulation.

Main Methods:

  • Development of S-PLUS functions for maximum likelihood estimation.
  • Conducting a Monte Carlo study to assess parameter estimate properties.
  • Analysis of sample size requirements for accurate estimation.

Main Results:

Related Experiment Videos

  • Sufficiently accurate ex-Wald parameter estimates necessitate sample sizes of at least 400, with larger samples potentially required for certain parameter ranges.
  • Shifted Wald parameter estimation is adequate with smaller samples (around 100), provided ill-conditioned fits are excluded.
  • The study examined the efficiency and bias of parameter estimates for these distributions.

Conclusions:

  • The provided S-PLUS functions facilitate the estimation of parameters for ex-Wald, shifted Wald, and ex-Gaussian distributions.
  • Sample size recommendations are crucial for reliable parameter estimation, particularly for the ex-Wald distribution.
  • The study highlights the importance of sample size in obtaining adequate parameter estimates for response time models.