Data from Thissen (1982); contains 5 dichotomously scored items obtained from the Law School Admissions Test, section 6.
References
Thissen, D. (1982). Marginal maximum likelihood estimation for the one-parameter logistic model. Psychometrika, 47, 175-186.
Author
Phil Chalmers rphilip.chalmers@gmail.com
Examples
if (FALSE) { # \dontrun{
dat <- expand.table(LSAT6)
head(dat)
itemstats(dat)
model <- 'F = 1-5
CONSTRAIN = (1-5, a1)'
(mod <- mirt(dat, model))
M2(mod)
itemfit(mod)
coef(mod, simplify=TRUE)
# equivalentely, but with a different parameterization
mod2 <- mirt(dat, 1, itemtype = 'Rasch')
anova(mod, mod2) #equal
M2(mod2)
itemfit(mod2)
coef(mod2, simplify=TRUE)
sqrt(coef(mod2)$GroupPars[2]) #latent SD equal to the slope in mod
} # }