My initial reaction is that if you have an operational definition of radical innovation, then you are not working in Grounded Theory.  You already have a theory which has allowed you to construct the operational definition.  

Having said that, there are no real parameters around Grounded Theory in that way.  there is nothing that said you need a wide range or a large sample.  But Grounded Theory would be best suited to look at the environments in which the radical innovation policies arose, rather than looking at the policies themselves.  And that would seem to suggest that th e way to look at the difference is to look at an equal number of situations in which radical innovation did not arise.  

It is not clear rational to use GT in this research. Since you have already selected the case study design, it is better to continue on the same line of thinking . If you are to develop a new theory, it is always necessary to review available theories and ask a question why you need to develop a  new theory(  no enough theories or the available theories are not sufficient to explain the phenomenon that you study).

Dear Devasheesh,

I agree with first answer (Ian Stuart) that GT is not suitable if your already place yourself in a givent theoretical approach (radical innovation). GT is thought to provide a methodological perspective to identify emergent categories and heir relationships from empirical evidence, rather than probing through cases previously established theories or resrarcher hypothesis. Saying that, I do not think than a number of cases (7 or other) is a problem at all, You might select as many cases as you want in your research design, BUT, not to predefined the research categories. Of course you have a theme you want to look at (innovation in health policy) but devise a methodology to grasp form epirical evidence how actors in those cases understand, conceotualize and create radical innovation in their own terms. GT should emerge from an interpretation of that material

Dears! as interpretive approach "every theory is false and every theory is at its right path so every theory could be in need of extention or construction, so an Interpretivist approach grounded theory could be used.

Mouna

I have to agree with the first 3 answers above; if you already have an operational definition, then you are not doing Grounded Theory which abstracts substantive theory from collected data ('grounds' theory in the data).

Perhaps Case Study is a better approach here; but I have to ask how you came by your operational definition of radical innovation in health policy. From commonalities of existing theory in 'the literature'? In which case you could compare this with data collected in your fixed number of cases (I'm assuming that project constraints dictate a fixed number of cases) and the difference is your substantive theory; of course there may be no difference in which case you will be supporting  existing theory.

Grounded theory is about discovery, not validation of a preconceived theory.  You go where the data (e.g. interviews, cases, stories) take you, and you build theory based on what you find.  The means of gathering data is open and can take various forms.  You may even revise your theory on the fly.  But building theory is hard; go in with your eyes open and expect far more work and time than for other designs.

I have mentored several successful GT studies, and a word to the wise (particularly for doctoral students) - only use GT is you have a compelling reason to do so.  It's a very demanding approach, and many students struggle with it.

Please also refer to the following sources, particularly: the major difference between Grounded Theory methodology and other research methodologies is that the former’s emphasis on theory development….people run the risk of using Grounded Theory methodology when they do not understand / overlook / misuse the procedures, and/or do not aim at developing theories (Strauss and Corbin, 1994, pp. 274, 277; Corbin and Strauss, 1990; Tan, 2010). Grounded theory methodology suffers from its apparent simplicity; it is not an easy task (Suddaby, 2006).

• Corbin, J. and Strauss, A. (1990) Grounded theory research: procedures, canons, and evaluative criteria, Qualitative Sociology, 13, 1, pp. 3-21.
• Strauss, A. and Corbin, J., (1994) Grounded Theory Methodology: An Overview, in Denzin, N. K. and Lincoln, Y. S. (Eds.), Handbook of qualitative research, Sage Publications, Thousand Oaks,  Chapter 17, pp. 273-285.
• Suddaby, R. (2006) From The Editors: What Grounded Theory Is Not, Academy of Management Journal, 49, 4, pp. 633-642.
• Tan, J. (2010) Grounded theory in practice: issues and discussion for new qualitative researchers, Journal of Documentation, 66, 1, pp. 93-112.  

Case studies are one of the qualitative approaches and you can use it as your research methods. Unlike quantitative studies, in the grounded theory you could not determine the sample size before conducting the study. Data analysis will say the point when the sampling is adequate (based on data saturation). Therefore, case study method is well matched with your aim.

Good Luck