There is a long-standing debate about whether students should focus on quality or quantity in order to improve their performance.
Here's the version I heard (it differs only slightly from the printed version):
On the first day of class, a pottery professor divides his class in two: The first group will be graded on quality—by the end of the semester, each person must produce one item which will be judged based on its quality. The other group will be graded purely on quantity—the total weight of all the items produced will be weighed with higher numbers given higher grades.
By the end of the semester, each person in the quantity group had produced works of higher quality than any of those produced in the quality group.
The second group had the opportunity to experiment and learn while the first was focused on refining an initial conception. The result seems less surprising when you think about it that way.