pcX {eba} | R Documentation |
Computes a paired-comparison design matrix.
pcX(nstimuli)
nstimuli |
number of stimuli in the paired-comparison design |
The design matrix can be used when fitting a Bradley-Terry-Luce (BTL)
model or a Thurstone-Mosteller (TM) model by means of glm
.
See Critchlow & Fligner (1991) for more details.
A matrix having (nstimuli-1)*nstimuli/2
rows and
nstimuli
columns.
Critchlow, D.E., & Fligner, M.A. (1991). Paired comparison, triple comparison, and ranking experiments as generalized linear models, and their implementation in GLIM. Psychometrika, 56, 517–533.
eba
, thurstone
, glm
,
balanced.pcdesign
, linear2btl
.
data(celebrities) # absolute choice frequencies btl <- eba(celebrities) # fit BTL model using eba summary(btl) y1 <- t(celebrities)[lower.tri(celebrities)] y0 <- celebrities[lower.tri(celebrities)] ## Fit BTL model using glm btl.glm <- glm(cbind(y1, y0) ~ pcX(9) - 1, binomial) summary(btl.glm) # BTL model does not fit these data! ## Fit Thurstone Case V model using glm tm.glm <- glm(cbind(y1, y0) ~ pcX(9) - 1, binomial(probit)) summary(tm.glm) # neither fits the TM model