There were four things that interested me about this dataset:
1. There was no correlation between years-to-degree and whether a student had an MS (from another institution) or a BS/BA degree at the start of the PhD program.
2. Most students needed more time than was covered by guaranteed financial support, but not much more (many needed ~ 1 year more).
3. When a colleague and I looked at the dataset and applied our qualitative and totally subjective evaluations as to which students were our most 'successful' (as in smart and hard-working, got awards/fellowships in grad school, published, got jobs after graduation etc.), we saw no trend in years-to-degree. Some 'successful' students zipped through the PhD program, finishing in 3-4 years; others took significantly longer.
4. Years-to-degree did not vary as a function of specific advisers. An individual adviser might have students who finished in 3-4 years and students who finished in >7 years.
Years-to-degree depends on a lot of factors, including (in no particular order):
- the nature of the project;
- the student's funding situation (TA, RA, no funding, continuous/discontinuous funding);
- the student's extent of research experience prior to starting the graduate program;
- the methods involved and access to necessary facilities or other support;
- whether there are any unforeseen setbacks;
- the student's work habits;
- the student's health (physical and mental);
- the presence or absence of personal crises or other significant events (weddings..), including those involving family, friends, or pets;
- the work environment (research group or department dynamics);
- the adviser's accessibility, level of interaction, sanity level;
- the amount of additional non-research responsibilities required (e.g., departmental service)
- number of degree requirements (courses, exams);
- whether preliminary exams are passed on the first try;
- expectations regarding number of published/submitted papers before graduation;
- presence/absence of a post-graduation job offer (and amount of time spent job hunting while a student);
- whether the student has an iPhone.