TwoPLM: Two-Parameter Logistic Model

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Two-Parameter Logistic Model

Description

The two-parameter logistic model is a classic model that defines the probability of a student with ability theta successfully answering item j, using both a slope parameter and a location parameter.

Usage

TwoPLM(a, b, theta)

Arguments

a	slope parameter
b	location parameter
theta	ability parameter

Value

Returns a numeric vector of probabilities between 0 and 1, representing the probability of a correct response given the ability level theta. The probability is calculated using the formula: P(\theta) = \frac{1}{1 + e^{-a(\theta-b)}}

exametrika documentation built on Aug. 21, 2025, 5:27 p.m.