Merge pull request #859 from amas0/master

Fix difficulty -> discrimination typo

src/stan-users-guide/problematic-posteriors.qmd

@@ -188,7 +188,7 @@ interpretable relative to student 1's ability to answer them.
 
 This solution is not sufficient to deal with the multiplicative
 invariance introduced by the question discrimination parameters
-$\delta_i$.  To solve this problem, one of the difficulty parameters,
+$\delta_i$.  To solve this problem, one of the discrimination parameters,
 say $\delta_1$, must also be constrained.  Because it's a
 multiplicative and not an additive invariance, it must be constrained
 to a non-zero value, with 1 being a convenient choice.  Now all of the