Samejima graded response model (alias of Grmsam)

Samejima's GRM is already implemented as Grmsam; this is the same estimator exported under the catalogue's second spelling and delegates to it rather than carrying a second copy.

Usage

Irtgrm(y, theta, a, b_k)

Arguments

y: Observed categories, 0-based (0 .. m).
theta: Person abilities, same length as y.
a: Item slope, positive.
b_k: The m strictly increasing thresholds.

Value

As Grmsam.

References

Samejima (1969), Estimation of latent ability using a response pattern of graded scores, Psychometrika Monograph Supplement 34(4, Pt. 2). doi:10.1007/BF03372160

Examples

Irtgrm(c(0, 1, 2), theta = c(0, 0.5, -0.5), a = 1, b_k = c(-1, 0, 1))
#> $estimate
#> [1] 0.2197239
#> 
#> $p_observed
#> [1] 0.2689414 0.1951151 0.1951151
#> 
#> $probs_first
#> [1] 0.2689414 0.2310586 0.2310586 0.2689414
#> 
#> $loglik
#> [1] -4.581593
#> 
#> $categories
#> [1] 4
#> 
#> $n
#> [1] 3
#> 
#> $method
#> [1] "P_k = P*_k - P*_{k+1} with logistic P*, Samejima (1969)"
#> 
#> attr(,"class")
#> [1] "morie_rich_result" "list"