posterior {MiscPsycho}R Documentation

IRT Posterior Density

Description

Compute the density of theta

Usage

posterior(x, theta, params, ind.dichot, control = list())

Arguments

x A vector of observed item responses
theta Ability estimate
params Item parameters organized as a list of lists
ind.dichot Indicator denoting which items in x are multiple choice
control A list of control parameters,
D
A constant usually fixed at 1.7 to bring the logistic function into coincidence with the probit
mu
Mean of the prior distribution
sigma
Standard deviation of the prior distribution
Q
Number of quadrature points used in the Gauss-Hermite approximation

Author(s)

Harold C. Doran

Examples

params <- list("3pl" = list(a = c(1,1), b = c(0, 1), c = c(0,0)),
               "gpcm" = list(a = c(1,1), d = list(item1 = c(0,1,2,3,4), item2 = c(0,.5,1, 1.5))))
posterior(x = c(0,1,2,2), theta = 1, params = params, ind.dichot=c(1,2)) 

[Package MiscPsycho version 1.5 Index]