Model-free estimation of a psychometric function


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[ci,sl0] = bootstrap_ci_sl(TH,r,m,x,N,h0,alpha,X,link,guessing,lapsing,K,p,ker,maxiter,tol);

Bootstrap estimate of a confidence interval at a significance level alpha for the estimated slope for the local polynomial estimate of the psychometric function with guessing and lapsing rates. The confidence interval is based on bootstrap percentiles.


TH: required threshold level

r: number of successes at points x

m: number of trials at points x

x: stimulus levels

N: number of bootstrap replications; N should be at least 1000 for reliable results

h0: bandwidth

Optional input:

alpha: significance level of the confidence interval; default is 0.05

X: set of values at which estimates of the psychometric function for the slope estimation are to be obtained; if not given, 1000 equally spaced points from minimum to maximum of x are used

link: name of the link function; default is 'logit'

guessing: guessing rate; default is 0

lapsing: lapsing rate; default is 0

K: power parameter for Weibull and reverse Weibull link; default is 2

p: degree of the polynomial; default is 1

ker: kernel function for weights; default is 'normpdf'

maxiter: maximum number of iterations in Fisher scoring; default is 50

tol: tolerance level at which to stop Fisher scoring; default is 1e-6


ci: confidence interval based on bootstrap percentiles

sl0: slope estimate

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