Propensity

Michael asks:
I recently had the following question marked wrong on a homework assignment where, among other words, we were required to use the word propensity, so I used the following sentence: "Many claim poor handwriting is a propensity for being a doctor." However, the student teacher who marked it wrong was unable to give an explanation as to why it was marked wrong, so I was wondering if you could help me with explaining why it was marked incorrectly.

Propensity, my dictionary tells me, means "a natural disposition or tendency...a liking for; partiality." So it's got to be a trait of a person, not of a skill like handwriting. If you turned the sentence around, however, it could work: "Doctors have a propensity for bad handwriting."