So, as an example, let's say that I have data on a small auction that I conducted.
Let's say I am selling a car and there are 5 bidders, and I have data on each of their bids, who won, who participated, etc. Now, let's say that I have 5 different cars, so the auction occurs 5 separate times. For example, in one auction, all 5 buyers participate while in another only 3 buyers participate. I am wondering how to model out this situation for expected revenue (continuous variable -> linear model), while accounting for which buyers were present. I am modeling the data for all 5 of the auction together, but want to account for the presence or absence of a buyer in an auction. Is this simply a matter of including a dummy variable for each buyer, where 0 is absent and 1 is present? Or is there some alternative solution like tree models or other advanced tools that can be utilized to examine this problem.
EDIT 1: I have more than 5 "auctions", but I just specified that number to keep things simple.
EDIT 2: I'd be interested in hearing about non dummy-variable solutions to this problem.