MediumStatisticsst-163

IRT 2PL Probability

Problem

Return the two-parameter logistic probability 1/(1 + exp(-a*(theta - b))).

Hint

The slope a is the item discrimination.

case 1

in: [0,1,0]

expected: 0.5

case 2

in: [1,1.5,0]

expected: 0.8175744761936437

case 3

in: [0,0.5,1]

expected: 0.3775406687981454

case 4

in: [2,1,-1]

expected: 0.9525741268224334

case 5

in: [0,2,0]

expected: 0.5

Starter codePython

import math
def irt_2pl_probability(theta, a, b):
    # Your code here
    pass

5 test cases · run your code against them in the editor