Papers which have a large amount of content in common are often restricted against each other. This means that you are normally unable to take both papers. For example, if you have passed STAT 110, you are normally unable to take STAT 115, as these papers are restricted against each other.
Details about any restrictions are listed against each paper in the Prescriptions section of the Guide to Enrolment, or on the individual paper pages on the University of Otago website.
Further information