R/IRTLikelihood.ctt.R

In TAM: Test Analysis Modules

## File Name: IRTLikelihood.ctt.R
## File Version: 9.07

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IRTLikelihood.ctt <- function( y, errvar, theta=NULL )
{
    N <- length(y)
    if ( is.null(theta) ){
        theta <- seq(-6,6,len=21)
            }
    TP <- length(theta)
    res <- matrix( NA, nrow=N, ncol=TP)
    errsd <- sqrt(errvar)
    for (tt in 1:TP){
        res[, tt] <- stats::dnorm( y, mean=theta[tt], sd=errsd )
        }
    attr(res,"theta") <- matrix( theta, ncol=1 )
    attr(res,"prob.theta") <- NA
    attr(res,"G") <- 1
    class(res) <- "IRT.likelihood"
    return(res)
}
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