## Wednesday, February 02, 2005

### Beware of Notation

I gave an exam today. Much the same as what you've come to expect from my students and my exams -- even after the whole pigeonhole principle quiz disaster, some of them still don't know what the pigeonhole principle is. As a whole, I think that the grades gave a pretty fair indication of the students' understanding of the material. A good exam overall.

Many students were done in by notation. I sort of knew that this would be a problem and put at the top of the exam the following:

Reminder: The notation Fn stands for "the nth Fibonacci number."

We had used this notation in class. I made a big fuss about it. We practiced with several examples and wrote the recurrence relation that defines the Fibonacci sequence. The notation came up in the homework. I made another fuss when we went over the homework.

Unfortunately for my students, they seem unable to tell the difference between Fn+1, Fn+1, F times (n+1) , and n+1. (If it isn't showing up well in HTML, these are: F_{n+1}, F_n +1, F \cdot (n+1), and n+1.)