I'd like to enhance that 5-point test a little...
0 – Penis does not enlarge.
1 – Penis is larger, but not hard.
2 – Penis is hard, but not hard enough for penetration.
3 – Penis is hard enough for penetration, but not completely hard.
4 – Penis is completely hard and fully rigid.
5 – Penis is so hard it can occasionally strike sparks against flint.Here's a PDF link to the longer 15-question
International Index of Erectile Function:
http://files.sld.cu/urologia/files/2011/08/iief.pdf