So often, we advertisers are faced with the very real dilemma of wondering if our ads work. The reality is, it's in the question where we do the most wondering. What on earth do we mean by work?
If a really popular ad generates an increase in sales, then by gosh, the ad worked. However, if an ad tests well, but a small flaw in the product is discovered, one can argue that the faster people stop buying the product would also be an indication of the ads effectiveness. To wit, an ad promotes trial, a bad product ensures there's no retrial.
In direct marketing, that's junk mail to the common folk, the communication is judged on how many people call. Indeed, depending on price point and other factors, if 3 people out of a 1000 call, the communication can be judged to have worked. Generally though, direct marketers think of 3-5% response as 'working'.
Things get a little tougher when the objective of the ad isn't as clear. Lets say your objective is an introduction. The ad says: introducing a new flavor from Tropicana. The simple fact is, the ability of the ad to work is directly tied with the shelf space that the store gives the product. An ad can create desire, bu the product better be there when the shopper heads to the store.
I say all this because of an article I read whereby things like vegetables taste better when wrapped in McDonald's wrappers. McDonald's has such positive brand equity amongst kids that things that aren't McDonald's foods taste better when wrapped in their brand. Interesting.