Dissertations can be based solely on the secondary data, without a need for the primary data. no research can be completed only using primary data and secondary data collection and analysis is compulsory for all dissertations.
Primary data collection methods can be divided into two categories: qualitative and quantitative.
they are critically analyzed to find answers to research question(s).
Secondary data, on the other hand, refers to a type of data that has been previously published in journals, magazines, newspapers, books, online portals and other sources.
The choice between the two depends on a set of factors such as the area of study, research philosophy, the nature of the research problem and others. Conclusive research design, on the contrary, aims to provide final and conclusive answers to the research question.
Conclusive research be further divided into two sub-categories. There are two types of data – primary and secondary.
In simple words, research phislophy refers to your beliefe about how data should be collected, analysed and used.
Accordingly, clarification of reseaerch philosophy is a starting point for the choice of research methods.
Phenomenology, on the contrary, takes into account subjective human interests and focuses on meanings rather than hard data.
You have to specify in your dissertation which philosophy you are following. Reseach methods also depend on the type of research accprding to the purpose of the study.