I have a large data set of 700 ebay auctions and want to examine seller reputation effects on auction revenue. some sellers have "detailed ratings" (about 45%), these ratings are out of 5 stars across four categories. i have all the data on detailed ratings for those that have them but of course i do not (because as it doesn't exist) have data for about 55% of the observations. I was looking at various ways to deal with the missing data as i really dont want to loose all of those observations. I was thinking to generate a dummy "HASDETAILEDRATINGS" coded to 1 if a seller has detailed ratings and then include the results of the four detailed categories for those observations that have them. would this be valid and if so how would i interpret coefficient results?
PS. if anyone can suggest a better way to deal with this problem i would be most grateful. thank you!