IRTpp (version 0.2.6.1)

probability.2pl: 2PL probability function

Description

The probability function in the 2PL model.

Usage

probability.2pl(z, a = z$a, b = z$b, theta, d = -a * b)

Arguments

z

Optional. A list with the parameters a and b specified by keys.

a

The discrimination parameter

b

The difficulty parameter. (Optional if d is specified)

theta

The subject's latent trait.

d

Optional. Overrides the b parameter, it is equal to -a*b. Used in some functions.

Value

Tue value of the probability for the model 2pl.

See Also

probability.1pl, probability.3pl, prob.3pl, prob.2pl

Examples

## Simulate the test
# data <- simulateTest(model = "2PL", items = 20, individuals = 200)
## item parameters
# zita <-data$itempars
## Latent traits
# thetas <- data$latentTraits
## Probability model
# probability.2pl(zita, theta = thetas)