To give some context: I'm quite new to quantitative research in social sciences and learned about IRT, Rasch Reliability and Wright-Maps yesterday.
Today a colleague sent me this image:
and asked how it could be, that a single item can have multiple difficulities associated with it (see the marked coordinates).
As i understand it the Wright-Map was constructed by first gathering the cognitive abilities of the students and then letting them go through a test. The difficulties (coordinates on the right hand side of the diagram) were constructed by correlating the test-results with the cognitive-abilities of the corresponding student using a Rasch-Reliability-test.
I couldn't find anything related on the internet and since i'm quite new to the field myself don't already have a full overview of resources i could utilize.
Can someone elaborate?