I am conducting a research at PhD level on cooperative learning in pakistan at schools level. In my research i am asking teachers’ perceptions about cooperative learning and their practices.i am confused about methodology, is this a phenomenology or grounded theory.As cooperative learning is a very new phenomenon in schools and if i am not wrong only very few people know about it. my research tools are Semi structured indepth interviews schedule for teachers , focus group discussions with students and class room observations . kindly help me out. till now I have conducted interviews with 21 private schools teachers and 25 government or public schools teachers . i want to ask about sample size also . what is the appropriate sample size for qualitative research.