The short answer is "about 6 years". But boy, do we have a long answer for you. 6 years? Wasn't I always told that the ave...

How long does it take to get a Ph.D at IIT Bombay?

14:04 Eeshan Malhotra 22 Comments

The short answer is "about 6 years". But boy, do we have a long answer for you.

6 years?
Wasn't I always told that the average Ph.D lasts about 5 years? We took a hard look at the data, and apparently, it doesn't. We examined data about all the Ph.Ds completed at IIT Bombay since 1990, and the average length is about 5.9 years. Ah, but you object, that's most likely due to outliers - the few students who take 8, or 10, or 14 (yep) years, to complete their Ph.D, and skew the mean.  Nope. The value of 5.9 is after taking care of all of these. In fact, the Civil Engineering department, which has the shortest average Ph.D length, clocks in at 5.1 years. CSE, at the longest, takes about 6.7 years on average.

Here's a visualization of all the students who have completed their Ph.Ds at IITB since 1990, classified by department, in order of the average Ph.D length:
[Click on image for better resolution]

Coincidentally, both the longest (14 years) and the shortest (2 years) have both been in Chemical Engineering.
Averaging across departments,  the distribution looks something like this:
[Click on image for better resolution]
Over 32% of the students took 6 years to complete their Ph.D

An interesting question to ask is whether the average length of the Ph.D has been constant over the years. Let's take a look.
Darkness of circle represents the number of students at that data point.

Wow! It looks like the average Ph.D length has been consistently decreasing! While the trend seems quite shocking at first, there are a couple of catches: First, the data from the earliest few years is drawn from very very few data points, and is extremely sensitive to aberrations. In fact, things seem to have stabilized quite a bit by 1995, which is a good reference. Second, a large number of Ph.Ds started in the last few years are still going on! So while it may seem that the average for 2011, for instance, is around 3.7, keep in mind that anybody who is planning to take over 4 years is still in the institute, and hence, not a part of the dataset at all. This reduces the apparent length for the last few years. This is the classic survivorship bias.

Ignoring these periods prone to errors or biases, for the period of 1995 to 2009, the average length seems to have stayed more or less constant - although, the number of outliers seems to have increased.

Hope you enjoyed our foray into data journalism. Do give us feedback on how to improve, in the comments section below. Look out for the next post very soon. In the meantime, if you're feeling adventurous, all code used to gather the data and create the visualisations has been open-sourced. Feel free to play with it and derive some great statistics of your own. Some more crazy visualizations on the dataset are here.


Footnotes:
1. Data for some departments has been combined in cases when the departments merged - e.g. IT with CSE, Bio-Medical Engineering with Biosciences & Bioengineering, and so on.
2. All data was sourced from Electronic Theses and Dissertations (ETD) Archives maintained by the Central Library, IIT Bombay. Every student's graduation year was scraped from the thesis, and their joining year calculated from their roll number. Some corrections were made manually. Huge thanks to the ETD for maintaining the archives and making them publicly available.



22 comments:

  1. next time could you post data on universities and higher studies or placements... cpi vs acceptance, por vs jobs etc..

    ReplyDelete
    Replies
    1. That sounds like an interesting analysis to do - any pointers on data sources?

      Delete
  2. Have you considered MSc - PhD students also?
    If yes then have to mistakenly considered their MSc years too since you have taken start year from roll nos.?

    ReplyDelete
    Replies
    1. For precisely that reason, the M.Sc+Ph.D students were excluded from this analysis.

      Delete
  3. This comment has been removed by the author.

    ReplyDelete
  4. Two short problems
    1. Many students "submit" their thesis for external review and then come back to defend after almost 6 months. This review period was longer in the past, because IITB insisted that comments from 1 foreign reviewer should be received before conducting the defense. Some time around 2007 or 2008, this policy changed, where the defense could be conducted once a majority of the reviewers have sent favourable reviews, irrespective of whether they were from India or not. This policy change has brought down the period between submission and defense to around 6 months.

    The point is, after submission of the thesis for external reviews, the students have absolutely no control over when their defense will take place. It may not be possible for you to dig this data out, but you should be truly looking at the time between enrollment and submission of thesis, not defense.

    2. Plus, if my defense is in January 2007 or December 2007, the end time remains the same in your computations. So, you are potentially adding almost a year to the completion time. Because PhD defense happen through out the year, unlike undergrads or Masters, who graduate on a fixed day.

    ReplyDelete
    Replies
    1. 1. Great point. I'll clarify that the periods are calculated till the time of the actual defence.

      2. We're also potentially SUBTRACTING a few months in some cases (for the very same reasons you stated). The point is that unless researchers have a proclivity to finish their Ph.Ds near the beginning or end of the year, the estimates will be unbiased, and over a large number of data points, the offsets will average to zero.

      Thanks for the feedback!

      Delete
  5. Also not all the PhD students enrolled at IITB are full-time researchers.

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    Replies
    1. This is correct. We would have loved to separate out these researchers, but given the data we have, we'll just have to live with an estimate across ALL Ph.Ds.

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  6. Please continue this exercise with no of publications, for all the PhD supervisors....This will help prospective students to choose the dept and guides!

    ReplyDelete
    Replies
    1. We're always looking for interesting analyses to perform with data! Although, it's important to remember that there are way more factors that influence individual cases.

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  7. I agree with Vinay's View. Should not consider time between thesis submission-Defense Viva and also from Defense viva-Convocation. Combining both would add-upto 10-12 months.

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  8. Regarding the separation of part-time and full time researchers, you can use the roll numbers to distinguish them. The number of digits used in the roll has changed from 2012, but I think the sequence was similar even before that. For e.g. consider a 2012 joinee with roll number 12-4-DD-C-xxx. Here 4 is PhD, DD is the Department code, C is Category (0-TA, 8-External etc). Prior to 2012, I believe they had only xx, while others remained same.

    ReplyDelete
    Replies
    1. Didn't know that! Let's see if I can manage to include something like that.

      Delete
  9. may i know how could you get the information about the PHD students from IITB from past many years. I too need this information. please help me with this.

    ReplyDelete
    Replies
    1. You should get in touch with the ETD department at the Central Library, IIT Bombay

      Delete
    2. You should get in touch with the ETD department at the Central Library, IIT Bombay

      Delete
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