After providing a definition of how "quality score" works, Bradd Libby tells us why the highest quality score isn't always the best. He writes that the formula is so simple it's surprising how
frequently people get it wrong.
"In fact, the purpose of all economic activity is to maximize profit, not clickthrough rate nor Quality Score," writes Libby. So, when performing tests of
competing ad creatives, we should judge them by the differences in profit they generate per impression, irrespective of the Quality Score values that Google reports."
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