Transformation of item and person parameters to the Bista metric.

Function uses output of equat1pl to provide two data.frames, one for the item parameters on the bista metric and one for the person parameter (PVs) on the bista metric.

Usage

transformToBista ( equatingList, refPop, cuts, weights = NULL, defaultM = 500, 
                   defaultSD = 100, q3bound= .2, roman = FALSE, vera = TRUE,
                   idVarName = NULL, years=NULL)

Arguments

equatingList: The object returned by equat1pl.
refPop: Optional: Data frame with at least three columns. First column indicates the domain name. Note that this name must match the domain names in the output of getResults. Second column contains the mean of the reference population. Third column contains the standard deviation of the reference population. Fourth column optionally contains the transformed mean on the Bista metric of the reference population. Fifth column optionally contains the transformed standard deviation on the Bista metric of the reference population. If the fourth and fifth columns are missing, values will be defaulted to 500/100. If refPop is not specified, mean and SD will be computed from the data, optionally using weights (if the weights argument is specified).
cuts: A named list with cut scores. Names of the list must match the domain names in the output of getResults. Each element of the list is a named list with one or two elements—the cut scores (in ascending order) and (optionally) the labels of the stages. The first element (cut scores) must be named values. The second element (labels of the stages) must be named labels. See the examples of defineModel for further details.
weights: Optional: a data.frame with two columns, first column is person identifier, second columns is individual caseweight. Necessary for the transformation of linking error for (ordered) factors and/or if descriptives of the reference population should be computed directly from the data. See the examples of defineModel for further details.
defaultM: Mean of the reference population on the “bista” metric.
defaultSD: Standard deviation of the reference population in the “bista” metric.
q3bound: Define the absolute boundary of Q3 values which should be captured in the item parameter list according to the guidelines of the “Vergleichsarbeiten”.
roman: Logical: Use roman numbers for competence level column in the shortened item parameter table dedicated for the “Vergleichsarbeiten”?
vera: Logical: Prepare item parameter list according to the guidelines of the “Vergleichsarbeiten”?
idVarName: Optional: character vector of individual student id. This is only to provide compatibility with older package versions. Specification of this argument is only necessary if the function gives an error.
years: Optional: numeric vector with two elements, indicating the both years of assessment. Only necessary if additional linking error object should be created.

Value

A list with three data frames: the first one contains original and transformed item parameters and competence levels. The second one contains original and transformed person parameters and competence levels. The third one contains transformation information.

Author

Sebastian Weirich

Examples

# see example 5, 6, and 6a in the help file of defineModel()