It's common for poll analysts to discuss the RCP average, and well-known that the RCP average is a simple arithmetic mean of the polls under consideration.
But what are the other rules? In particular I'm interested in:
What rules govern how many polls should be averaged (this seems inconsistent between various types of elections RCP is currently covering)?
What rules govern whether a poll will be included in the RCP average?
What's the minimum number of polls that needs to be available before they will publish an average?