align_raw {scaleAlign}

Scale Alignment Methods

Description

Apply scale alignment methods to sets of item parameters and other model information provided by the user. These functions may be used to apply scale alignment to output from other item parameter estimation programs such as ConQuest. Note that dda1 and dda2 both require user-provided unidimensional and multidimensional item parameters.The lrafunction requires user-provided sufficient statistics, thresholds, and the number of observations and response categories per item. The function lra2 is a wrapper for lra that computes some needed quantities from a user-provided data set.

Usage

dda1(
  multi_pars,
  uni_pars,
  itemtype,
  item_ind,
  dim_ind_i,
  refdim = 1,
  alpha = 1
)

dda2(
  multi_pars,
  uni_pars,
  itemtype,
  item_ind,
  dim_ind_i,
  refdim = 1,
  alpha = 1
)

lra(
  multi_pars,
  itemtype,
  ss,
  nobs,
  ncats,
  thresh_m,
  item_ind,
  dim_ind_i,
  refdim = 1,
  alpha = 1
)

lra2(dat, multi_pars, itemtype, item_ind, dim_ind_i, refdim = 1, alpha = 1)

Arguments

multi_pars

Vector of estimated multidimensional item parameters, to be rescaled.

uni_pars

Vector of estimated unidimensional item parameters, must be in the same order as multi_pars.

itemtype

Item type: "1PL", "PCM", or "PCM2", see align.

item_ind

Vector with one element for each parameter indicating which item each parameter is associated with.

dim_ind_i

Vector with one element for each item indicating which dimension each item is associated with.

refdim

Which is the reference dimension (unchanged during alignment)

alpha

Vector of dimension steepnesses (often set equal to 1). Recycled if alpha is of length 1.

ss

Item sufficient statistics as proportions of examinees who reach each step, see align. Should be of the same length as multi_pars.

nobs

Number of observed (non-missing) data points for each item.

ncats

Number of response categories for each item.

thresh_m

Vector of Thurstone thresholds. Should be the same length as multi_pars and ss.

dat

Data set with items as columns and examinees as rows. This data set must be the same data set used to estimate item parameters.

Details

See align.

Value

List with the following elements

rhat

Vector of estimated scaling parameters r

shat

Vector of estimated shift parameters s

alphatilde

Vector of transformed dimension steepnesses

new_pars

Vector of transformed (i.e., aligned) item parameters

thresh

Vector of aligned Thurstone thresholds