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The most of qualitative researchs are based on interpretive paradigm that their principles differ from positivism paradigm and quantitative
research. Therefore, qualitative researchers should be aware of exertion the concepts and criteria of the research that roots in positivism paradigm. They should look at these from perspective of existentialism and epistemology of interpretive paradigm.
One of the major challenging and ambiguous that qualitative researchers confronted, is the validity in qualitative research. The article examines this subject from various views.