upstate29651 said:
RoddyFreeman said:
gregg75 said:
Looks like those PPMs aren't as acurate as they were "promised" to be.
Could there be the possibility of manipulation of data (somewhere)?
http://arbitron.mediaroom.com/index.php?s=43&item=797
I doubt it's manipulation of data. From what I've heard, it's probably more related to the sample,
proper ethnic weighting, etc.
Explain this "proper etyhnic weighting".
G
If a market is (say) 20% black, then ideally your panel will be 20% black as well--assuming your demo data to begin with is correct; ATL got burned on overestimated Census figures, especially with Latinos, last year. One controversial shortcut is to apply a factor to come up with the proper weighting; for example, if your panel is only 10% black, then the ratings of those panelists will be weighted double, and everyone else will be weighted less to compensate.
Of course, there are limits to how much of this can be done; if sample size gets too small, then reporting may be incorrectly magnified. For example, what would be the effect on the final numbers if you have only 2 black panelists (out of 100, making for a 2% black panel) and they both listen to WGST all day? Now you have 2% of the market making up 20% of your ratings (and they looove WGST).
Now blow this out among all demos tracked in the market, and all the possible associated factoring.