* Funding: Securing funding (grants, assistantships) can impact timelines. Students who secure funding early and consistently may finish faster. Delays in funding can prolong the process.
* Research progress: Research can be unpredictable. Unexpected results, difficulties collecting data, or problems with analysis can all add time.
* Coursework requirements: The specific program's coursework requirements can vary. Some programs might have more intensive coursework than others.
* Dissertation writing: Writing a substantial dissertation is a major undertaking and can take a considerable amount of time.
* Individual student factors: Individual student's work habits, writing skills, and overall productivity play a large role.
While 4-5 years is a common target, it's not uncommon for students to take longer, especially if they encounter unforeseen research challenges or need to take additional coursework. Therefore, a range of 4-7 years is a more realistic expectation.