More on Quality Score

After three pages explaining Quality Score, you’d think I’d have nothing else to say on the matter. But there is a few other things you should know and keep in mind about the QS.

In the previous sections, I showed how Adwords ranks ads by using your bid and CTR to calculate an ad rank. This ad rank in turn is used to calculate how much each advertiser pays. As mentioned, Google does not use CTR but QS. The calculations are all the same, simply use QS instead of click rate as I have done in those calculations.

But the QS you see in your account is a whole number between one and ten. It is very doubtful that Google uses those actual whole numbers. The QS that Google uses has much more precision and contains many decimal places. So, in Google’s eyes, your QS is more likely a number between 1.00000 and 9.99999, the QS you are shown rounded off. I also suspect that QS goes beyond ten in actual rank and price calculations. In the How Does Adwords Work section, I mentioned that CTRs are smoothed out to remove the effects of position. Mathematicians have words for this smoothing out called normalizing. This is done so that every advertiser is on a level playing field, no matter which position their ad is served, first or forty-first. Being in lower positions, ads are generally clicked less often, in absolute terms, than those in higher positions. It would not make sense to use the ad’s absolute CTR in the QS and subsequent calculations.

Quality score is also calculated relative to all advertisers for that keyword. This in fact is the whole concept of QS and one which you must know and understand. It is so important, it’s why I’ve highlighted this whole paragraph in blue.

It means that your QS is an indication of how well you are doing against advertisers using that same keyword. Google calculates QS in the following manner:

An average click rate is calculated for all advertisers using that keyword. This is the historical click rate for that keyword, not just active advertisers. This average click rate is of course normalized by position as well. Then, your own CTR is compared to the average and a QS calculated which depends on how far away – positively or negatively – you are from that base line. This is done using standard deviation calculations with the mean assigned a QS. For the sake of argument, let’s say that baseline- the average QS – is five. Note that it could be any number but five is more likely since it is between one and ten.

Knowing your own QS, you can tell whether your CTR is average, below average or above average compared to other advertisers. For that keyword. At that position.

That is very powerful information to have. This means that even with a CTR you may consider low, say 2%, if your QS is 8, you are doing well because the average is five. It means your two percent click rate is not that bad.

In a linear system, all advertisers would fall somewhere on the line from first to last, best to worst. In other words, if your QS was 10, you would know you were THE best. But, a QS of 10 only means you are ONE of the best. You may not be the only one with that QS. In fact, you likely are not.

Since the QS is a calculation of how far away you are from the mean, it is possible that all advertisers fall between say 5 and 7, with no one below or above those values. Of course, you don’t know other advertisers’ QS. So the best you can do is to improve your click rates to get a better score.

Most advertisers likely fall near the mean and most advertisers likely have a QS of between 4 and 7 (assuming the mean is set at 5). The percentage will vary from keyword to keyword and how many advertisers there is, but probably 60% of advertisers fall within that range. Another 20% would be eight and above, the other 20% below. Again, these are assumptions. But if you have a Great QS (8 and above), you are indeed in rarefied air and can assume you are in the top tier of the best click rates.

Google says they now calculate Quality Score for each search. This is likely done after the search and not during since that would require a lot of processing power. This means that, even if no advertiser makes any changes whatsoever, all advertisers will see their QS change no matter if the searcher clicks on ads or not. This change will be minute but a change nevertheless. Over time, these will accumulate and eventually you may see your QS go up or down by a whole number.

Finally, you may be wondering that if QS is effectively CTR, what does Google do when you add a new keyword or new ad? After all, it doesn’t know your click rate until the ads actually run. It appears that they will assign an average QS. Once your ad has enough impressions, the QS is adjusted in the normal way after each search.

It also appears that the system makes some calculations on your ad. You may therefore see a jump or decrease in QS soon after creating a new campaign even though there are no impressions. Google probably makes sophisticated analysis comparing your ad to those of other advertisers with similar ads. They do after all have ten years worth of data they can check. New keywords which nobody has used before, which is extremely unlikely, are probably assigned an initial QS based on similar keywords. Therefore, even if you were the only advertiser for that keyword, it is unlikely you will get a QS of ten right away. Your ad still needs to prove itself. That is why when adding a new keyword that you will rarely see your QS of ten right away. The system does need data to figure it out.

Resume of Quality Score

made u-p of three components: the keyword’s CTR, the relevancy of the keyword to the ad and landing page and landing page factors,
calculated for each keyword-ad combination,
smoothed out to remove effects of position has on your absolute click rate,
assuming a perfect score on the relevancy and landing page components, which should be easily attained, your QS is in effect your CTR. Achieve higher click rates and you will get a higher quality score,
Google shows your QS as a whole number between 1 and 10 but is actually calculated to many decimal places,
is calculated based on the average of all advertisers. It is therefore an indication of how well you are doing compared to others,
is not linear. Most advertisers will fall within a certain range with a small minority falling below or above that range,
is recalculated after each search for that keyword. Your QS and that of all advertisers is constantly changing, however slightly. Over time, these small changes accumulate and will eventually be seen with a change of your whole number QS.

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