The prior mode was named vague, yet it put Normal(0, 0.1) on discrimination and difficulty. Fixed-question experiments, a prior sensitivity check and a 434-student simulation show how that shrinkage tracked sample size.

tc-SVD applied to handwritten digits, faces and four clustering benchmarks, with the numbers reported as they are, including the data sets where other methods won.

One exam and its mathematics lesson had four legitimate student counts: 521, 530, 522 and 523. How request identity, applicability filters, seen-blank versus unseen coding and a silent library helper decided who and what entered an IRT calibration.