This is the meat of your paper!! You are going to repeat this statement verbatim several times throughout your paper and your appendices. The purpose statement has seven  required parts:
1. Research method is identified as qual, quan, mixed, case.
2. Research method is appropriate to the proposed study.
3. Research design is clearly stated.
4. Research design is appropriate to the research method.
5. Research variables are briefly identified.
6. Specific population group of proposed study is identified.
7. Geographic location of study is identified.
The Purpose of the Study section of chapter 1 should be 2-3 paragraphs long, provide a reflection of the problem statement, and identify how the study will be accomplished. This section explains how the proposed study will contribute to the field. The section begins with a declarative statement, "The purpose of this study is....” Included in this statement are also the research design, population, variables (quantitative) or phenomena (qualitative) to be studied, and the geographic location. Further, the section clearly defines the dependent and independent variables, relationship of variables, or comparison of groups for quantitative studies. For qualitative studies, this section describes the nature of the phenomena to be explored. Keep in mind that the purpose of the study is restated in other chapters of the dissertation and should be worded exactly as presented in this section of chapter 1.
Creswell (2003) provided some sample templates for developing purpose statements aligned with the different research methods (qualitative/quantitative/mixed method).
Creswell, J. W. (2003). Educational research: Planning, conducting, and evaluating quantitative and qualitative research (2nd ed.). Thousand Oaks, CA: Sage.
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