eap: Function to estimate ability using EAP algorithm

In talentlens/talentlens: R package for team TalentLens

Description

Takes a named score vector and a data frame with known item parameters, and returns the estimated theta.

Usage

eap(x, params, D = 1.702)

Arguments

x	Vector with correct responses coded as 1 and incorrect responses as 0. NOTE: the values need to be named with item ids
params	Data frame with unique item names and corresponding item parameters on each row, NOTE: columns need to be named "id", "a", "b" and "c"
D	Scaling constant D (Defaults to 1.702 for normal ogive model)

Details

The theta estimation algorithm is based on the implementation of the EAP algorithm in the GetFeedback platform. Instructions from Louis-Charles Vannier.

An alternative to using this function is eapEst from the catR package.

Value

Estimated theta value.

Author(s)

Morgan Strom

See Also

eapEst eapSem

Examples

#Create named score vector
score_vec <- c(1,1,0,1,0)
names(score_vec) <- c("item1", "item2", "item3", "item4", "item5")

#Create parameter data frame
params <- data.frame(id = c("item1", "item2", "item3", "item4", "item5"),
                     a = c(0.7, 0.8, 0.9, 1, 1.1),
                     b = c(-2, -1, 0, 1, 2),
                     c = c(0,0,0,0,0))

#Estimate theta
theta <- eap(score_vec, params)

#Using the function for a matrix with 4 observations
score_mat <- matrix(c(1,1,0,1,0,
                      1,0,0,0,0,
                      1,1,1,1,0,
                      1,1,1,1,1),
                    nrow = 4, ncol = 5, byrow = TRUE)
colnames(score_mat) <- c("item1", "item2", "item3", "item4", "item5")

thetas <- apply(score_mat, 1, eap, params=params)

talentlens/talentlens documentation built on May 31, 2019, 2:52 a.m.