theta_ll function

theta_ll

returns the log of the likelihood of theta, given a vector of item responses, item parameters. Note that this is the simple ll - it is the continuing product of the response probabilities. It includes a hack, that will nudge the raw response to the first item to adjust for zeros and perfects. This should be updated to work with adjusted raw scores instead...

theta_ll(theta, responses, itemParams)

Arguments

• theta: a scalar value of theta.
• responses: a vector of item responses (used in a call to pX).
• itemParams: a list of item designs (each used in a call to simplef). Must be of same length as responses.

Returns

a double, the log of the likelihood at theta..