Comparing PR and advertising is like lumping together apples and oranges.
Because advertising messages and placements can be controlled, it's not wise to use the same devices to measure PR, cautions Dr. Walter K. Lindenmann, senior VP and director of Ketchum's Research and Measurement Department.
Unlike the CPM model used in advertising, PR measurement relies on these variant tools: media analysis, cyberspace analysis, trade show and event measurement, polls and surveys, focus groups and/or ethnographic studies. (Ketchum, 212/448-4411)