The PhD dissertation, or thesis, is the most challenging part of getting an advanced degree. It is assumed that the PhD student is capable of handling the work associated with graduate courses. The thesis is designed to show that the student is ready to conduct independent research. The PhD thesis topic must be chosen carefully: it should be of sufficient importance to justify the degree, while being sufficiently limited in scope to allow completion within a reasonable amount of time.
What Makes a Bad Thesis?
Choosing a good thesis topic is key to graduating on time; a poor choice may result in adding years to the degree. So what makes a poor thesis topic?
The student is not interested in the topic
A thesis is a significant document, representing hundreds of hours of work. Choosing a topic that the student is not genuinely interested in will make it very difficult to sustain interest long enough to complete the research. It also makes it more difficult to convince the thesis committee that the topic is interesting!
The topic is not significant
The standard by which a PhD thesis is judged is that it must make a "significant contribution to the literature;" whether the work is significant is judged by the student’s committee. In general, something that is published in a peer-reviewed journal can be assumed to be significant. However, it is always best to obtain the advance approval of the committee members, as any one of them can declare the topic to be not significant; by obtaining their approval first, it is unlikely they will quibble over the significance of the work later.
The topic is overly broad
While the work needs to be significant, it is still recognized that this is student work: it is expected to be at the level of a new PhD in the field, not an established researcher. Tenured professors have time to embark on speculative, multi-year projects with an uncertain payout; graduate students do not. The PhD thesis topic should be chosen so that the work can be completed in a reasonable amount of time (what is reasonable will vary by field) with an expectation of publishable results. Leave the seminal papers for later; the point now is to produce solid research that meets the minimum standards for publication.
What Makes a Good Thesis?
So what should you look for when choosing a thesis topic?
You and your advisor find the topic interesting
While it’s certainly possible to finish your degree if this isn’t true, it will be a lot more difficult. When you and your advisor are both engaged in the topic, it will be easier to get advice and stay on top of your research. A topic your advisor is opposed to will slow you down greatly.
You are familiar with the field
By the time you choose a thesis topic, you’ve most likely been in school for a number of years. Even if you returned to graduate school after time in the workforce, you’ve most likely taken classes before choosing a thesis topic, and in some disciplines you will have passed a research exam. Take advantage of what you’ve learned: if your research topic is in an area that you’re already familiar with, you’ll have a much easier time with the literature review as you’ll understand the terminology being used. Otherwise, expect to spend a fair amount of time learning the basics of the field before you can begin your research.
The problem has interest (but not too much)
On the one hand, you don’t want to choose a problem that nobody cares about; if you do, solving it may not be judged to be a significant contribution. On the other hand, if many people are working on the problem, it is likely that either the problem is not solvable or someone else will solve it before you do. The best topic will be in an area that people in your field are interested in, but where you have reason to believe you have a new approach that will be successful.
Keep your committee in the loop: they may have valuable suggestions, and it’s always better to hear objections earlier rather than later!
Your thesis proposal is a contract, but it’s not set in stone. It represents an agreement that the work you plan to complete is worthy of a PhD; however, that doesn’t mean you have to follow the plan exactly. If your original approach doesn’t work out or new avenues present themselves, your research plan can be amended.
Make frequent backups of your thesis and all your materials. When the inevitable computer crash arrives, you’ll be glad you did.