LEARNING ABOUT ARBITRON QUESTION: I'm PD/MD in a small market. I was fortunate to reach this position fairly early in my career. There are a few things I was not able to pick up from my previous PDs, though. Where and how can I learn more about Arbitron numbers and what they mean, and programming with that in mind? DAN REPLIES: Arbitron offers periodic "schools" for PDs, devoted specifically to using their ratings information. For info, go to: http://www.arbitron.com/pdadvantage/seminar_sched.htm.