For example, the following course formats are proposed at the same department of the same university (the list is not complete):

 - 12 credits (48+72 hours)
 - 9 credits (24+12 hours)
 - 9 credits (24+0 hours)
 - 6 credits (24+36 hours)
 - 0 credits (one lecture; those are not really courses, but are included in the course catalog as bonus content to make up a bit for courses not offered in the current year)

All of the courses I refer to are Master's level. "x+y" hours means x hours of lectures and y hours of practical sessions.

Intuitively, one would suppose that the number of credits should be somehow proportional to the number of hours.