obsInf {catSurv} | R Documentation |
Calculates the observed information of the likelihood of a respondent's ability θ for a given item
.
obsInf(catObj, theta, item)
catObj |
An object of class |
theta |
A numeric or an integer indicating the value for θ |
item |
An integer indicating the index of the question item |
The observed information is equivalent to the negative second derivative of the log-likelihood evaluated at θ. This function should never be called when the respondent has answered no questions as the likelihood is not defined.
The function obsInf
returns a numeric value of the observed information of the likelihood, given θ, for a given question item.
This function is to allow users to access the internal functions of the package. During item selection, all calculations are done in compiled C++
code.
Haley Acevedo, Ryden Butler, Josh W. Cutler, Matt Malis, Jacob M. Montgomery, Tom Wilkinson, Erin Rossiter, Min Hee Seo, Alex Weil
## Loading ltm Cat object data(ltm_cat) ## Store example answers setAnswers(ltm_cat) <- c(1,0,1,0,1, rep(NA, 35)) ## Calculate observed information for different ability parameters and items obsInf(ltm_cat, theta = 1, item = 10) obsInf(ltm_cat, theta = 1, item = 11) obsInf(ltm_cat, theta = 0, item = 10) obsInf(ltm_cat, theta = 0, item = 11)