djh101 wrote:What if you didn't just get an A+ but did exceptionally well in the course, e.g. got the highest grade and exceeded the average by a very large amount (in stat mech I got 100% on the midterm, which averaged around 50%)?
In my opinion and from advice from my professors, letters about class performance generally go on a lower tier than letters from research supervisors. If you have to get a letter from an instructor (it's hard/rare to get all 3 letters from research since research opportunities are hard to find), the type of letter mentioned above would be the best kind to get. That is, one that distinguishes you from the rest of the class. But generally, even if you are several standard deviations above the mean in Stat Mech, that doesn't really provide a ton of useful information about whether or not you are going to be a good graduate student. There are tons of empirical evidence for students with bad grades doing excellent research. So I would only get a letter like this if I could not find one about my research ability.