sensR (version 1.5-2)

samediff: Computation of tau and dprime for same different test

Description

Computation of tau and dprime and their uncertainties for the same different test using maximum likelihood.

Usage

samediff(nsamesame, ndiffsame, nsamediff, ndiffdiff, VCOV = TRUE)

Arguments

nsamesame

The number of same-answers on same-samples

ndiffsame

The number of different-answers on same-samples

nsamediff

The number of same-answers on different-samples

ndiffdiff

The number of different-answers on different-samples

VCOV

Should the variance-covariance matrix of the parameters be computed. Defaults to TRUE.

Value

An object of class samediff with elements

coef

named vector of coefficients (d-prime and tau)

vcov

variance-covariance matrix of the coefficients

se

named vector with standard error of the coefficients (standard error of d-prime)

data

a named vector with the data supplied to the function

test

a string with the name of the test (same-different)

call

the matched call

convergence

convergence indicater. 0 indicates convergence. For error codes see optim.

logLik

Value of the log-likelhood at the MLE of the parameters.

case

A case indicator for internal use

Details

The function computes the maximum likelihood estimates of tau and delta.

References

Christensen, R.H.B., Brockhoff, P.B. (2009). Estimation and inference in the same-different test. Food, Quality and Preference, 20 pp. 514--520

Examples

# NOT RUN {
# data: 8 of the same samples were judged to be same
#       5 of the same samples were judged to be different
#       4 of the different samples were judged to be same
#       9 of the different samples were judged to be different

samediff(8, 5, 4, 9)
# }