John Wanamaker, who founded one of the first department store empires in the United States, famously complained that half his advertising was wasted; he just didn't know which half. Today, businesses can better track the return on their marketing dollars by vigorously testing their message. Indeed, the improvements and breakthroughs in testing tools make it possible to experiment with virtually every element of a business's public marketing efforts and see results quickly.
Perhaps the most well known testing concept is the A/B split test: two nearly identical ads are shown to customers, with one variable changed, to determine which version performs better. Typical variables include headlines and price points. The history of advertising is replete with stories of how altering a headline—or even a single word of copy— resulted in a dramatic spike in response. Case in point: When a book on auto repair was marketed to mechanics with the headline, "Fix any part of any car," the ad failed. But when it was tested with a new headline that said, "Fix almost any part of almost any car," sales of the book skyrocketed.