title: Determination of optimal data placement for psychometric function estimation: a computer simulation.
abstract: Psychometric functions are used to relate the responses of a subject to physical stimuli in a variety of psychophysical tasks. However, it is time consuming to obtain data to determine a psychometric function if many stimulus levels and many trials are required. A computer simulation was conducted to determine the minimum number of data points needed for such a determination. The computer simulation also determined the optimal placements of the stimuli and the number of trials per datum point for psychometric function determinations. Results indicate that a 2-point sampling method with 30-50 trials per point at optimal locations can produce a psychometric function with accurate spread and threshold estimates in a yes-no paradigm. However, the 4-point sampling method yields statistically smaller variances of the estimates. For the 2-alternative forced-choice paradigm, at least 120 trials per point are needed for the 2-point sampling method's estimated parameters to differ from the known parameter values by less than 5%. The simulation results suggest that 3-alternative or 4-alternative forced-choice is preferable to 2-alternative. Furthermore, when a criterion-free paradigm is not required, the yes-no paradigm is a better procedure than m-alternative forced-choice for obtaining the corresponding psychometric function because of smaller standard deviation of the estimates and smaller number of trials/point required.
authors.affiliation: Department of Biometry and Epidemiology, Medical University of South Carolina, Charleston 29425, USA. lamcf@musc.edu
authors.forename: C F
authors.initials: CF
authors.lastname: Lam
authors.forename: J R
authors.initials: JR
authors.lastname: Dubno
authors.forename: J H
authors.initials: JH
authors.lastname: Mills
mesh_terms: D003198:Computer Simulation; D006801:Humans; D008954:Models, Biological; D010812:Physical Stimulation / Q000379:methods*; D011594:Psychometrics / Q000706:statistics & numerical data*; D011601:Psychophysics