The duped metric measures, for students who submitted more than one submission to an exercise, how many of those students saw a duplicated SCT error message. 

The duped metric is an "internal" metric, in the sense that the Content and Engineering teams are responsible for it, as it directly measures the quality of SCTs, as written by Content Developers. 

However, it can be informative; analysis revealed that a high duped metric is correlated with both a high '% asked hint' and high '% asked solution.'