Quality Score Can Mess Up Split Testing

Google likes its advertisers to show their better-performing ads more often. If you never venture into the Campaign Settings area and change it, Google will "sunset"  your low CTR ads by default. AdWords ad serving settings

In AdWords For Dummies I offer several compelling reasons to move the radio button from "Optimize" to "Rotate" (to show the ads more evenly, so you can more quickly and accurately determine the results of your split tests).

In a perfect world, you could choose "Rotate" and know that each ad was getting equal air time – over a period of 7 days, for example, Ad 1 and Ad 2 would both get roughly 6500 impressions each. As long as the impressions are about equal, the split tests are valid and the ultimate measure of an ad’s effectiveness – profit per 1000 impressions – is valid as well.

Quality Score: a wrench in the works

Trouble is, Google’s quality score metric gets in the way here. Different ads with different quality scores get shown in different positions – ads with poor quality may get shunted to page 2 or 3, or not get shown at all. So your scientific split test to find out which ad is favored by prospects, or which one makes you the most money, is now seriously skewed if Google determines the two ads are of different quality.

To make matters worse, Google doesn’t tell you the quality of an individual ad. Quality scores are attached to keywords only, and the quality of a keyword is the same as the quality of that keyword in relation to the worst ad. In other words, if the keyword "inflatable cordless phone" triggered one ad with the headline "Inflatable cordless phone" and another with the headline "Give your dog viagra", then the quality score for that keyword would be "Poor" because of the poor fit with the second ad.

The Tony the Tiger Solution

If all your quality scores are "Great," that means all your ads in that ad group are "Great." Like blue eyes, baldness, and susceptibility to poison ivy, "Great" is a recessive trait. They all have to be great for your keyword to be great.

And it’s pretty easy to make your ads highly relevant to your keywords. Use the keyword phrase a couple of times in the ad, preferably the headline, maybe even in the URL.

But of course, if your landing pages aren’t also highly relevant and part of high quality Web sites, you still won’t know if your ads are of the same quailty. So like much of AdWords, and advertising, and business, and life, you need to feed, weed, and water the entire system. If your ads aren’t getting an equal number of impressions despite chosing "Rotate," then your first task is to get the quality scores of all your keywords to Great.

Here’s how:

  1. Peel and stick to create tightly focused keyword lists
  2. Match keyword lists to highly relevant ads
  3. Match ad groups to highly relevant landing pages


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  1. #1 • Gemma Laming said on July 29 2011:

    I could imagine you as Tony the Tiger!