How are the targets set for an web based support center (ie for Email and chat supports)?. Is there any scientific way of setting the targets or its just the experience that sets the standards?. Also, how do one monitor quality of response of an email response. We have some standards want to understand how others are doing it.

I understand this is different from call center kind of monitoring, is there any thing that we can apply in all forms of support?

Thanking in advance,
Manohar