Item Information Function for 3PLM
Arguments
- a
slope parameter
- b
location parameter
- c
lower asymptote parameter
- theta
ability parameter
Value
Returns a numeric vector representing the item information at each ability
level theta. The information is calculated as:
\(I(\theta) = \frac{a^2(1-P(\theta))(P(\theta)-c)^2}{(1-c)^2P(\theta)}\)
