Hello Letitia,
No, it is not considered rude to ask a coach about their credentials. In fact, a good coach will be pleased that you are taking the hiring of a coach seriously enough to ask. There are two independent coach certification organizations: the IAC (International Assn of Coaches)
www.certifiedcoach.org and the ICF (International Coach Federation)
www.coachfederation.orgAs you may know, certification is not required for coaches (although it is a plus). There are many excellent coaches who are not IAC or ICF certified, but asking a prospective coach about their certification, training, experience, and references is just good business.
I happen to be a certifier for the IAC; if anyone would like more information on coach credentials please don't hesitate to contact me through my website
www.becomeacertifiedcoach.com