Can one use the same objectives and hypotheses in their PhD thesis taken from another PhD thesis but different data sets? (Even the state is different.)

  • What do you mean, the state is different?
    – Sursula
    Sep 3, 2023 at 7:05
  • This seems unlikely. But your advisor can answer this. Is the methodology different or just the data?
    – Buffy
    Sep 3, 2023 at 10:24

2 Answers 2


At least in applied science it might be possible. But objectives can be tweaked to state what additional differentiation the new data set brings. Different populations, bigger region covered or exploring if the results from previous research are transferable to new data set

  • 3
    It doesn't seem like it is adequate for a doctoral thesis. Maybe for a masters.
    – Buffy
    Sep 3, 2023 at 19:47
  • Here is an example: whether a new kind of drug works for a disease. Previous study had a dataset of 100 patients from Texas. Now I am looking for impact on efficacy of drug in a closer climate and have 100 patients from Alaska. The primary objective is still efficacy of drug. This definitely can be expanded to a dissertation
    – Anuj
    Sep 3, 2023 at 19:57
  • 2
    You have a different hypothesis, I think. Something around the lack of relationship to climate (or something, maybe not climate). Still skeptical. Especially at the doctoral level. What is new? What is the contribution? I would certainly ask for more from a student. It seems to lack any evidence of experimental design. I'd be fine with it as undergraduate thesis since execution of an experiment teaches something.
    – Buffy
    Sep 3, 2023 at 20:01

The devil is in the details --- talk to your supervisor and panel

There is nothing inherently wrong with research that explores an existing question and hypotheses using new data; that is potentially valuable research because it gives us new evidence bearing on a research question. However, in a PhD candidature the standard requirements for successful completion are that the research must be significant, original, and extend knowledge in the field. Depending on the scope of the new data you collect for your project, what you are proposing might be considered insufficient or borderline in terms of "significance" and "originality". This really depends on the details --- if you collect a substantial amount of new data that really adds to the research area then this might by sufficiently significant and original to justify some good publications and the award of the degree.

I recommend you talk you your PhD supervisor and panel about your proposal to get their view on the significance of your proposed research. You should also bear in mind that PhD referees might see things differently to your supervisors, so you should remain cognisant of the danger that a referee might see your research as being insufficiently significant or original to warrant the doctoral degree. Personally, I think that a project that collects a significant amount of new data for re-analysis of an existing research question could be a significant contribution warranting a PhD degree, but others may have a different view.

Another thing to bear in mind here is that it would be unusual for you to go through a research project spanning several years and not come up with any ideas for even minor tweaks of existing methods for your research. Even using a different data set might involve some new available variables or other differences that immediately lead to some new ideas for methodological tweaking. You might find that as you progress through your new analysis you have some ideas for how to refine methods/models in ways that are different to previous research, and this would potentially add to the originality of your research. If you decide to go with this proposal, be on the lookout for these things as you progress your project.

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