+ wishlist Add to Cart The item has been added Author: Remo Ostini Michael L. Nering Polytomous Item Response Theory Models (Quantitative Applications in the Social Sciences) [9780761930686] Buy More - Save More. Below are the available bulk discount rates for each individual item when you purchase a certain amount Quantity Price Savings 25 - 49 3% 50 - 99 4% 100+ 5% List Price As Low as $55.00 Format: Paperback