Recommendation letters

This post is the second episode featuring Prof. Mor Harchol-Balter's talk advising people applying to PhD programs in computer science or related areas.
[first episode - full article]

"Perhaps the most important part of your application is the letters of recommendation. You will need 3 letters of recommendation for the Ph.D. program, and typically 4 letters of recommendation for a fellowship.

Whom to ask for a letter
Ideally you would like to make all your letters of recommendation count. Consider the following two letters:

• Letter 1: “I highly recommend student X for your graduate program. Student X received an A+ in my undergraduate algorithms class. He was ranked Number 2 out of 100 students. He got the highest score on the final. He worked very hard all semester, never missed a class, and was always able to answer the questions that I asked in class. This conscientious attitude makes him an excellent candidate for any graduate program. ”
• Letter 2: “I highly recommend student Y for your graduate program. Student Y received a B in my undergraduate algorithms class. He was ranked Number 29 out of 100 students. Halfway through the semester we started working on network flows. Student Y seemed extremely excited by this topic. He disappeared for 4 weeks and even missed an exam. However when he came back, he showed me some work he had been doing on a new network flow algorithm for high-degree graphs. He had done some simulations and had some proofs. I’ve been working with student Y for the past couple months since then and he is full of ideas for new algorithms. I think student Y’s initiative makes him an excellent candidate for any graduate program.”

Which letter do you think is stronger? It turns out that Letter 2 is very strong. Letter 1 actually counts as 0. At CMU we mark all letters like letter 1 with the acronym D.W.I.C.. This stands for “Did Well In Class” which counts for 0, since we already know from the student’s transcript that he did well in class. By contrast, student Y’s letter gives us a lot of information. It explains that the reason student Y didn’t do better in class was that he was busy doing research. It also tells us that student Y started doing research on his own initiative, and that he is quite good at doing research. The professor was impressed enough with student Y’s ideas that he took him on as a student researcher despite student Y not having high grades. You want your letters to all be of type 2 (this doesn’t mean that you should skip class!). Remember that letters of type 1 will not count. You want words like 'self-motivated', 'strong research potential', 'own initiative', 'independent', and 'driven' to appear in your letters. These are the words that we circle when reading recommendation letters. You therefore want to ask letters from people who have seen you do research. These may be professors or employers.

One caveat: It makes some difference whom you ask for a letter. As a general rule (there are always exceptions due to people’s fame), letters from professors count the most. Next highest are letters from research scientists. After that come letters from lecturers, systems scientists, employers, or postdocs. Please do not get a letter from a graduate student. If you found yourself doing research where you were supervised by a graduate student or postdoc, you should ask the professor for whom they work if she can co-write the letter. The reason is simple: professors are the ones reading the letter, and they are most likely to know other professors.

There is an issue for students who have been working for a while. You will certainly want a letter from your employer, but you will also want two letters from professors. This was an issue for me when I applied to graduate school. What I did was to keep touch with a few professors during my time at work. When I was ready to apply to graduate school, I contacted the professors who knew me well and scheduled a meeting with them to discuss the research that I had done while I worked. I gave them each an oral presentation. I also gave them each writeups of each of my projects.

How to ask for a letter
Asking for a letter of recommendation won’t be a problem if you have been doing research with this person, but that won’t be possible in every case. Here’s a guideline which will maximize the contents of your letter. This works on the theory that professors have very little time and little memory (both of which are good assumptions):

1. Prepare a packet for each recommender. This packet should contain all the relevant information about you that could help the recommender. Be careful not to make the packet too large. Here’s what should be in it:
   • Your statement of purpose.
   • A summary of every research project you worked on and with whom, regardless of whether this was at a school or research lab. If you have published a paper, or have a technical report, please include that too.
   • A sheet of paper listing all math/cs/engineering/science classes you have taken with the names of professors and grades.
   • A list of extracurricular activities and awards/competitions.
   
   At the top of the packet should be:
   • A recent photo of you – professors receive many such packets and don’t remember you the second after you leave the office.
   • Directions. E.g., please seal and sign and send to this address by Jan. 5. Put an earlier date than the real deadline – professors are notoriously late.
   • Confirmation information: Please send me email at blank address after you send this off. If I don’t hear from you by Jan. 5th, I will send you an email reminder. (You need this confirmation information because otherwise you’ll never know if the recommendation was sent and you’ll be sitting around biting your nails wondering.)
2. Go to your potential recommender with your packet and ask him/her the following question: “Do you feel comfortable writing a strong letter of recommendation for me to graduate school?” You need to phrase the question this way so that the potential recommender has a way out. Do not be upset if the potential recommender says no. It is good that he/she let you know. This is much better than getting a weak letter.
3. Check with the school to confirm that they have received a letter from each of your recommenders.
4. Remember to at least send your recommender a thank you card! It’s a lot of work to write a decent recommendation letter, and you may need more letters in the future."