How long is a PhD thesis?

How long is a PhD thesis?

One question I did ask myself before I started to write up was “How Long is a PhD thesis”. If like me you did your PhD under a new PI, you more than likely will not have examples from previous PhD students that submitted thesis from the lab. Having previous students and postdocs in the lab will give you a wealth of information about how a professor likes the structure of their PhDs theses, how long they like you to spend writing up, will they publish your papers before your PhD thesis, who will your external examiner be (a collaborator or a competitor)? Because I was one of the first students to leave the lab it left me with a lot of questions about the PhD thesis such as how long is a PhD thesis? Along with other questions such as:

How long is a PhD thesis introduction chapter?

How do I write a materials and methods section?

How do I write a PhD thesis conclusion?

Because I found out the hard way about many of the questions above I thought I would give some responses and hopefully answer some of your questions about the PhD thesis. To help with the process I have provided links to my PhD in two parts (I couldn’t upload it in one file, be easy on the spelling mistakes!)

PhD thesis part I – Introduction, materials & methods, chapter 1 and some figures

PhD thesis part II – Results chapters & Conclusion

Before I delve into some of the questions I thought I would share the figure below by Marcus Beck outlining how long the average dissertation based on discipline. If like me you are a life science researcher the average length is around 150 pages, however, this can increase or decrease in length depending if you are a history of statistics graduate student.

How do I write a materials & methods section

I know I have jumped the first question here but before you start writing any other chapter of your PhD thesis I would definitely recommend beginning with the materials and methods section. The materials and methods section is the engine of your thesis and can be anywhere from 10 to 50 pages depending on the amount of protocols you carried out during your research.

As writing goes, the materials & methods section will be the easiest to write. If you have documented your experiments or know what papers or protocols you took them from or adapted from, it should be straight forward writing up your materials & methods section of your thesis. Personally I think it took me a few days, 3 to 4 and most of the time was spent on formatting and ensuring consistency.

Three tips I that I think should help you write your materials and methods sections are:

Focus on your main experiments first that where highly used throughout your PhD, you more than likely will be able to write them from memory.

Ensure decimals, symbols and measurements are correct and are consistent throughout i.e 2ml vs 2mL vs 2 mL.

Write your materials and methods section chronologically, if you look at my thesis you should see that I start with experiments that I use in the first results chapter and finish with experiments I carried out in the third results chapter.

How do I write a PhD thesis introduction?

Depending on what type of thesis you are submitting how long a PhD thesis introduction is can vary. For instance in some European countries, students submit 3 journal style papers for their PhD thesis so only require relatively short introductions. However, if you are writing an Irish/British or Northern American style thesis you might have a longer 30 page introduction.

The idea of the introduction should be to give the read all knowledge required to read the rest of your thesis and come to a conclusion. Therefore should cover a brief history of your research area, an overview of the disease model or research model studied and signaling pathways involved. For instance my PhD was on a signaling pathway in mitosis, so I broke my introduction down into a few sections:

The disease model my research was based on, treatment & drugs available

Signaling pathways that result in this disease

An overview of signaling pathways that were directly related to my research

The whole idea of the introduction section is to give your examiner a taste of things to come, then when you get to your results chapter you can give an detailed insight into signaling pathways involved in your research.

How do I write a PhD thesis conclusion

At this stage you are probably really tired of thesis, trying to meet a deadline to submit and looking for something to write in the conclusion. What I tried to do with my PhD thesis conclusion was to give a brief overview of what I had discussed in the previous chapters and then give my own personal input into the area and what I thought was important. At the end of the day a PhD thesis is your body of work and thoughts, so explaining your points, giving new hypothesis based on your research and giving a direction for further research.

18th Dec 2020 Sean Mac Fhearraigh

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