N. Jeremy Hill developed statistical methods for fitting psychometric functions with a collaborator. Their work examines sampling, goodness of FIT and the behavior of parameter estimates. A fitted threshold is consequently an inference from a model and sampled responses, rather than a directly observed immutable boundary of perception. The author name follows the original paper. [ref]
The psychometric function: I. Fitting, sampling, and goodness of fit by Felix A. Wichmann and N. Jeremy Hill. 2001, fitting and simulation methodology
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