gstudy {gtheory} | R Documentation |
gstudy
estimates variance components attributable to objects of measurement (e.g., persons) and facets (e.g., items and raters), as well as unexplained variation.
gstudy(data, ...) ## S3 method for class 'data.frame' gstudy(data, formula, colname.strata = NULL, colname.objects = NULL, keep.mer = F, ...) ## S3 method for class 'univariate' gstudy(data, formula, colname.strata = NULL, colname.objects = NULL, keep.mer = F, ...) ## S3 method for class 'multivariate' gstudy(data, formula, colname.strata = NULL, colname.objects = NULL, keep.mer = F, ...)
data |
a data frame in long format with a column for item scores and columns for sources of variance |
... |
additional arguments to be passed to |
formula |
a formula specifying the model to be estimated by |
colname.strata |
an optional string that specifies the name of the column containing strata (if conducting a multivariate G study) |
colname.objects |
an optional string that specifies the name of the column containing objects of measurement for calculating observed-score covariance (if conducting a multivariate G study) |
keep.mer |
a logical indicating whether or not to store the output from |
an object of class "gstudy
" that lists variance components of class "components
". It will also list observed-score variance and covariance between strata if you specify the names of the columns identifying strata and objects of measurement.
data.frame
: G study of a data.frame
object
univariate
: G study of a univariate
object
multivariate
: G study of a multivariate
object
Brennan, R. L. (2001). Generalizability theory. New York: Springer.
Rajaratnam, N., Cronbach, L. J., & Gleser, G. C. (1965). Generalizability of stratified-parallel tests. Psychometrika, 30(1), 39-56.
#Conduct a univariate G study. #Compare to results on page 116 of Brennan (2001). data(Brennan.3.2) formula.Brennan.3.2 <- "Score ~ (1 | Person) + (1 | Task) + (1 | Rater:Task) + (1 | Person:Task)" gstudy(data = Brennan.3.2, formula = formula.Brennan.3.2) #Conduct a multivariate G study. #Compare to results on page 270 of Brennan (2001). data(Rajaratnam.2) formula.Rajaratnam.2 <- "Score ~ (1 | Person) + (1 | Item)" gstudy(data = Rajaratnam.2, formula = formula.Rajaratnam.2, colname.strata = "Subtest", colname.objects = "Person")