Finds (A, B) of theta_T = A theta_F + B minimizing squared
differences between test characteristic curves of the common items
(plink Eq. 15), with transformed from-scale parameters a* = a_F/A,
b* = A b_F + B, c* = c_F. The symmetric variant adds the
reverse-direction term.
Usage
morie_linkqp(items_from, items_to, symmetric = FALSE, theta_points = NULL)
Arguments
- items_from, items_to
Matrices (or lists) of common-item 3PL
parameters (a, b, c) on each scale; use c = 0 for 2PL.
- symmetric
Minimize F1 + F2 instead of F1 only.
- theta_points
Optional evaluation grid (default 41 points on
[-4, 4]).
Value
A list with elements A, B, criterion,
symmetric, n_common, method.
References
Stocking, M. L. and Lord, F. M. (1983). Developing a
common metric in item response theory. Applied Psychological
Measurement, 7, 201-210. Weeks, J. P. (2010). JSS, 35(12).
Examples
M <- matrix(c(1, 2, 3, 4, 5, 6), nrow = 2)
morie_linkqp(M, M)
#> $A
#> [1] 1
#>
#> $B
#> [1] 0
#>
#> $criterion
#> [1] 0
#>
#> $symmetric
#> [1] FALSE
#>
#> $n_common
#> [1] 2
#>
#> $method
#> [1] "Stocking-Lord characteristic-curve linking (plink Eq. 15)"
#>
