mirt (version 1.6.1)

LSAT6: Description of LSAT6 data

Description

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.

Examples

dat <- expand.table(LSAT6)
head(dat)
model <- mirt.model('F = 1-5
                     CONSTRAIN = (1-5, a1)')
(mod <- mirt(dat, model))
coef(mod)

#equivalentely, but with a different parameterization
mod2 <- mirt(dat, 1, itemtype = 'Rasch')
anova(mod, mod2) #equal
coef(mod2)
sqrt(coef(mod2)$GroupPars[2]) #latent SD equal to the slope in mod