The 6-point test evaluates the validity of the estimated difference scale. Given 6 values, a, b, c, a', b', c', on the stimulus scale, if the pair $(a, b) > (a', b')$ and $(b, c) > (b', c')$ then it must be that $(a, c) > (a', c')$, where the symbol $>$ is taken here to mean is judged more different than. Given the observer's difference scale and $\sigma$ estimate, the likelihood of the choices made is calculated based on the link function indicated in the mlds object.
Usage
lik6pt(x, Six.Pts, ...)
Arguments
x
an object of class 'mlds', typically created by mlds
Six.Pts
a list of 3 data.frames, with names A, B, E. Each data.frame corresponds to a sample from a difference scaling experiment. The corresponding rows of the three data.frames yield the triples of trials that provide a 6
...
currently unused.
Value
Returns the likelihood of the observer's responses for all of the 6-point conditions from a given data set. As currently implemented, it returns a 1x1 matrix.
References
Maloney, L. T. and Yang, J. N. (2003). Maximum likelihood difference scaling. Journal of Vision, 3(8):5, 573--585, http://journalofvision.org/3/8/5/, doi:10.1167/3.8.5.