Mathematics has nothing to do with service quality and impact. Maybe, you are looking for a questionnaire, a scale, or stuff like that.

https://www.researchgate.net/post/How-can-we-measure-Service-Quality-SQ

For knowing the public service quality, there are various variables, of course some will be quality and some quantity. Consult a statistician to work out the impact of those variables.

Babak Jamshidi

yes I am looking for a quantitative scale and method allow me to measure the service quality

If you use quantitative scale(i.e.Likert scale) to measure public service quality and organizational impact, then you can make use of regression analysis