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Primary source: Usually a report by the original researchers of a study (unfiltered sources)
Secondary source: Description or summary by somebody other than the original researcher, e.g. a review article (filtered sources)
Conceptual/theoretical: Papers concerned with description or analysis of theories or concepts associated with the topic
Anecdotal/opinion/clinical: Views or opinions about the subject that are not research, review or theoretical (case studies or reports from clinical settings)
Books, Articles, & Web Pages
The text is especially useful for inexperienced student-researchers and doctoral students in the early stages of preparing a dissertation. The early chapters of the text clearly describe the process of selecting a problem, reviewing the literature, constructing a hypothesis, identifying and labeling variables, and constructing operational definitions. The later chapters assist students in refining methodological procedures, analyzing data, and writing the final research report