Is it good to state one weakness in a motivation letter for a PhD application?

Another answer I wrote at Quora.

A2A. Unless you think that’s a weakness that really needs explaining or that’s a weakness that actually explains your motivation to do a PhD, I see no reason to state it in your motivation letter.

A weakness that really needs explaining is a weakness that is so glaring and important, that it alone would prevent you from getting an offer. So, you try to explain to try to have a chance. Even so, don’t write too much about it. It may sound like an excuse.

A weakness that explains your motivation could be a good thing in some cases, even it may be risky to do that in your motivation letter. In my case, I wasn’t able to overcome a problem I found during my professional career. Something like that may be considered a weakness, right? After all, it’s not a case of success, but failure.

But after that, I became very interested in learning about ways to solve that problem. In turns out that the problem I was trying to solve is a major issue for Marketing research. So, I had to explain a weakness I had in order to show how a PhD could help me to achieve my goals.

Even so, don’t waste much time with your weaknesses. If a school is interested in you and about your explanations for a weakness, they will probably do that during an interview. During my interviews, they asked questions about the weaknesses they perceived in my application profile. Even weaknesses I had not thought about.

How do I talk about my research interests in a letter of motivation?

I'm posting here too an answer I wrote at Quora.

Since motivation is a very personal thing, writing about research interests also is. So, everyone will write in a different way, with no clear-cut and strict rules. Avoid using templates, for example.

But my suggestions are:

1 - Describe your research interests. If your research interests are too broad, they will not tell much about you. If you just tell that you are interested in doing research about Marketing while applying to a Marketing program, for example, it’s just a waste of time. But if you are too specific, it may also be a problem. A research interest that is too specific is also very limited, narrowing opportunities like finding a good advisor for you. If you know a little about research, you can describe that interest in a more academic way, like a research problem.

2 - Tell why you are interested in doing research, and why that subject you described. Telling them “why” will help them to understand your motivations.

3 - If you are interested in something, probably you already know something about it and have some experience to tell. It’s harder to convince someone that you are interested in something if you have never done anything about it. So, write a little about your knowledge and experience.

4 - Why should someone care about your research interests? Doing that kind of research will help your career, the university, companies, countries, the world?

5 - How do you think the program you are applying to can support you in your research interests? A faculty with similar interests? Access to data which are relevant for your interests? Laboratory and equipment?

Learning R

Now, it feels like a countdown, getting closer to the D-day. I've taken take of necessary things I could related to my application and enrollment.

I'm taking the time to study. One of the things that I was told to learn is R, a programming language and software used mostly for statistics. I found some books and websites, but starting to learn R can be quite overwhelming. 

So, I started an online course at Coursera. It's called Statistics with R and was developed by Duke University. It is still a little confusing at times, I think some things should be explained better. But at least there is the possibility of discussing the problems with other people, so I don't get stuck.