Compute theta for unidimensional models

Usage

compute_unidimensional_theta(a, b = 0, g = 0, i = 1, d = 1.702, theta = 0)

Arguments

a: numeric discrimination parameter
b: numeric difficulty parameter
g: numeric guessing parameter
i: numeric inattentiveness parameter
d: numeric scaling constant usually a value 1.749 or 1.702
theta: numeric or vector theta

Note

when scaling constant=1 it has no effect in equation
when inattentiveness=1 and guessing=0 function computes a 2PL score
when inattentiveness=1 and guessing!=0 function computes a 3PL score
when inattentiveness!=1 and guessing!=0 function computes a 4PL score

Examples

compute_unidimensional_theta(a=10,b=0)
#> [1] 0.5
x<-seq(-3,3,by=.01)
plot(compute_unidimensional_theta(a=5,b=0,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=5,b=-1,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=5,b=1,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=0,b=0,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=1,b=0,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=10,b=0,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=10,b=0,g=0,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=10,b=0,g=.1,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=10,b=0,g=.5,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=10,b=0,g=0,i=1,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=10,b=0,g=0,i=.9,theta=x),x=x, ylim = c(0, 1))

plot(compute_unidimensional_theta(a=10,b=0,g=0,i=.5,theta=x),x=x, ylim = c(0, 1))