Thanks again for the quick answer!
This is what my syntax looks like:
set constraints=cases;
datafile data_distr.dat;
format responses 9-31;
labels << labels_dist.lab;
score (1,2,3,4) (1,0,0,0) !item (16);
score (1,2,3,4) (0,1,0,0) !items (3,4,5,10,11,13,18,20,22);
score (1,2,3,4) (0,0,1,0) !items (1,2,6,12,14,19,23);
score (1,2,3,4) (0,0,0,1) !items (7,8,9,15,17,21);
codes 1,2,3,4;
model item;
estimate;
When conquest stops calculating, it says "Item thresholds are not available for models without discrete and increasing scores, within item multidimensional models, models with non-integer scores, or models with null categories".
When I look at the characteristic curves by category, I get a "smoothed" line for the correct response and only one "smoothed" line for the incorrect responses. But what I want is a "smoothed" line for every category.
What am I doing wrong?