Stopping rules in Bayesian adaptive threshold estimation



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Alcalá Quintana, Rocío and García Pérez, Miguel Ángel (2005) Stopping rules in Bayesian adaptive threshold estimation. Spatial Vision, 18 (3). pp. 347-374. ISSN 0169-1015

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Threshold estimation with sequential procedures is justifiable on the surmise that the index used in the so-called dynamic stopping rule has diagnostic value for identifying when an accurate estimate has been obtained. The performance of five types of Bayesian sequential procedure was compared here to that of an analogous fixed-length procedure. Indices for use in sequential procedures were: (1) the width of the Bayesian probability interval, (2) the posterior standard deviation, (3) the absolute change, (4) the average change, and (5) the number of sign fluctuations. A simulation study was carried out to evaluate which index renders estimates with less bias and smaller standard error at lower cost (i.e. lower average number of trials to completion), in both yes–no and two-alternative forced-choice (2AFC) tasks. We also considered the effect of the form and parameters of the psychometric function and its similarity with themodel function assumed in the procedure. Our results show that sequential procedures do not outperform fixed-length procedures in yes–no tasks. However, in 2AFC tasks, sequential procedures not based on sign fluctuations all yield minimally better estimates than fixed-length procedures, although most of the improvement occurs with short runs that render undependable estimates and the differences vanish when the procedures run for a number of trials (around 70) that ensures dependability. Thus, none of the indices considered here (some of which are widespread) has the diagnostic value that would justify its use. In addition, difficulties of implementation make sequential procedures unfit as alternatives to fixed-length procedures.

Item Type:Article
Uncontrolled Keywords:Adaptive methods; Sequential procedures; Stopping rules; Threshold estimation; Yes–no; 2AFC; Simulation
Subjects:Medical sciences > Psychology > Experimental psychology
ID Code:35710
Deposited On:19 Sep 2016 09:05
Last Modified:19 Sep 2016 09:05

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