Super introduced the variables of congruence and maturity. Determining and establishing a professional (vocational) choice, Super (1955) calls it “vocational maturity”, explaining that only interests and early choices are immature conditioning a choice but this should not be taken too seriously.
..we have to find / to develop questionnaire regarding the "stability of professional choosing" but you have to eliminate the variability which are coming from "congruence" - is the importance of professional roles compared to other roles in life.
Super, D.,E. Vocational maturity theory: Toward implementing a psychology of careers in career education and guidance. Measuring vocational maturity for counseling and evaluation. Washington, DC: National Career Development Association. 1974, p. 245
Provide a little more on the background, demographics of subjects, etc. and purpose/intentions as well as intended target groups and target group sample size... things like that, and may be able to help a bit. Did something similar when I was Dean of all graduate studies, Dean of Social Sciences, and Director of the IRAS (research capability). Thanks.