How can we apply "Six Sigma" in 'Service-Quality' phase of CRM (Customer Relationship Management), as most of the time 'Customer Responses' are Non-Quantifiable ?"

There are ways and means of quantifying a customer response through a well defined survey.

For example one such survey question is -

How would you rate your satisfaction with our solution provided on a scale of 1 to 10 where 1 stands for pathetic and 10 stands for outstanding?