R/sX2.R

In joakimwallmark/PolyOptimalIRT:

# Computes S-X^2 for polytomous items
sX2 <- function(O, E, N, maxTestScore, itemMax) {
    sx2 = 0
    for (k in (itemMax+1):(maxTestScore-itemMax)) {
        for (z in 1:(itemMax+1)) {
            sx2 <- sx2 + N[k]*(O[k, z]-E[k, z])^2/E[k, z]
        }
    }
    sx2
}