mirt (version 0.8.0)

fscores: Methods for Function fscores

Description

Computes MAP, EAP, ML (Embretson & Reise, 2000), EAP for sum-scores (Thissen et al., 1995), or WLE (Warm, 1989) factor scores with a multivariate normal prior distribution. Will return either a table with the computed scores and standard errors, the original data matrix with scores appended to the rightmost column, or the scores only. By default the latent means are set to be 0 for each factor, and the covariance matrix is set to the identity matrix, though these can be overwritten.

Usage

fscores(object, rotate = "", full.scores = FALSE,
    method = "EAP", quadpts = NULL, response.vector = NULL,
    degrees = NULL, returnER = FALSE, mean = NULL,
    cov = NULL, verbose = TRUE, scores.only = FALSE)

Arguments

object

a computed model object of class ExploratoryClass, ConfirmatoryClass, or MultipleGroupClass

full.scores

if FALSE (default) then a summary table with factor scores for each unique pattern is displayed. Otherwise the original data matrix is returned with the computed factor scores appended to the rightmost column

rotate

rotation declaration to be used when estimating the factor scores. If "" then the object@rotate default value is used (only applicable to ExploratoryClass objects)

method

type of factor score estimation method. Can be expected a-posteriori ("EAP"), Bayes modal ("MAP"), weighted likelihood estimation ("WLE"), maximum likelihood ("ML"), or expected a-posteriori

quadpts

number of quadratures to use per dimension

mean

a vector for custom latent variable means. If NULL, the default for 'group' values from the computed mirt object will be used

cov

a custom matrix of the latent variable covariance matrix. If NULL, the default for 'group' values from the computed mirt object will be used

degrees

the degrees argument to be passed to iteminfo, only necessary for multidimensional models when method = 'WLE'

response.vector

an optional argument used to calculate the factor scores and standard errors for a given response vector that may or may not have been in the original dataset

returnER

logical; return empirical reliability estimate as a numeric value?

verbose

logical; print verbose output messages?

scores.only

logical; return only the factor scores (only applicable when full.scores = TRUE)

References

Embretson, S. E. & Reise, S. P. (2000). Item Response Theory for Psychologists. Erlbaum. Thissen, D., Pommerich, M., Billeaud, K., & Williams, V. S. L. (1995). Item Response Theory for Scores on Tests Including Polytomous Items with Ordered Responses. Applied Psychological Measurement, 19, 39-49 Warm, T. A. (1989). Weighted likelihood estimation of ability in item response theory. Psychometrika, 54, 427-450.

Examples

mod <- mirt(Science, 1)
tabscores <- fscores(mod)
fullscores <- fscores(mod, full.scores = TRUE)
fullscores <- fscores(mod, full.scores = TRUE, method='MAP')
scores <- fscores(mod, full.scores = TRUE, scores.only = TRUE)
head(scores)

#calculate MAP for a given response vector
fscores(mod, method='MAP', response.vector = c(1,2,3,4))

#use custom latent variable properties (diffuse prior for MAP is very close to ML)
fscores(mod, method='MAP', cov = matrix(1000))
fscores(mod, method='ML')