The GRE contains an "Analytical Writing" section that is supposed to be a good indicator of .. something. But what? This is what I would like to know.
Is the score relevant to how well a student might do with some important aspects of graduate school? I took the GRE long before the advent of the Analytical Writing (AW) component, so I don't have any firsthand experience with it. I've read some of the available materials about what it is and how it is graded, and all of my recent graduate students have taken the AW exam, but I don't really know what the score means, if anything.
From what I've seen, the GRE in general does not predict whether a student will do well in research. This is not news to many (most?) people. The Quantitative score does tend to predict how a student will do in quantitative courses, but that may or may not correspond to whether a student can apply quantitative techniques in research. I've advised students with perfect Q scores and apparently no ability to think about science in a quantitative way or apply quantitative skills to research. I've advised students with lower Q scores who were quite talented at quantitative research applications.
Also based on personal experience advising students, I surmise that the Verbal score seems to indicate something about the complexity of an individual's vocabulary, but doesn't predict anything about reading/writing ability. Maybe that's where the AW exam comes in, but I still don't know what the score really means.
An exam involving writing and text analysis should test some skills that we want a grad student to have, but I have increasingly encountered extremely smart and creative students who write well and have no problem with reading comprehension but who have low AW scores, and students with high AW scores who struggle with writing and synthesizing essential points from what they read.
The conclusion that some smart students take tests well and some don't seems inevitable; this is of course one of the oft-proposed interpretations of student performance on standardized exams that are taken with strict time limits.
I don't think the GRE scores are totally meaningless. I would be very reluctant to admit a grad student with low scores on one or more of the GRE exam components unless the low scores were convincingly different from the rest of the academic record.
I have recently been gazing at applications with AW scores ranging from 3 to 6, and in many cases there seems to be no correlation between the AW score and the rest of the application, even for students for whom English is the first language. I am willing to believe that a 6 (out of 6) means the student is a good writer, just as I am willing to believe that a student with across-the-board good GREs is smart, but then there are all the students with good-but-not-great scores. I have seen no evidence that a student with an AW score of 5 (or even lower) is necessarily less-great at the things supposedly tested by this part of the exam.
In any case, we get these scores as part of grad applications, we stare at them, we try to figure out what they might mean, we consider them in the context of the entire application, and then we make our best guess in the admissions process based on the entire file.
2 years ago