# CTR is important - but why does this not make sense?

3 replies
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I know CTR is important when it comes to quality scores, but does Google measure quality score by average ad position and help work out the quality score like this, because I have a keyword in a campaign that I have been running since August, has only spent a small amount of money and averaging Position 5.

The lifetime CTR of this keyword is 0.42%, and in the last 7 days it's been 0.17%. But guess what the QS is???

10 out of 10 ?!?

This is annoying, not because it is 10 out of 10 (obviously), but because knowing everything I do about QS (which evidently can't be that much), I am completely baffled at how this could have a QS of 10.

It makes me wonder if all this optimising of my adwords campaigns is 1) Correct, and 2) Worth the effort ?!

What on earth is going on?! :confused:
• Your CTR is compared to the historical CTR of that keyword, at that position. Basically, it's a simple standard deviation calculation.

Example. A keyword has had an historical average of 2%. That's the starting point and if your CTR is 2%, your QS will be 5. The standard deviation calculates to 0.2%. For every 0.2% CTR above or below 2%, you gain or lose a QS point. So if your CTR is 2.6%, that's 3 standard deviations above the mean therefore your QS is 8.

It doesn't matter which position you are in. The calculation is the same and the mean CTR and SD figured out for that position.

If you got a QS of 10, all it means is that your CTR is at least 5 SDs above the mean. That means you're doing very well indeed. It doesn't matter what your actual CTR is, 10% or 0.5%, you are compared to the historical average. If the average was 12% and yours was a seemingly high 12%, your QS will be 5. In other words, your 0.42% is pretty darn good for that keyword at that position because other advertisers have had a hard time matching this.

Just looking at a CTR means nothing. It has to be put into context. The QS does that for you, placing a value to how well you are doing against competitors, no matter your position.

Other notes about QS. Only Google's search data is used in the calculations, not the search partners. Display campaign data is not used either if you mix search and display in the same campaign, which you shouldn't do. That's a different QS calculation.

As you are in fifth position and a QS of 10, I would suggest to increase your bid. You'll likely get shown over the SERPs and more people click those. It seems less and less people click ads on the right side. Your CTR will probably increase ten-fold and at minimal cost because of your high QS. In fact, your CPC may not be that much higher.
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This is a great response. Thank you very much!

A couple of questions:

This standard deviation can't simply be applied to CTR alone, can it? As QS is more than just good CTR.

Also, my CTR for the last 7 days has gone down by almost 250%. Doesn't quality score get re-evaluated? I would have expected a drop since the historic CTR is clearly much better than this.
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•  Originally Posted by thetruth23 This standard deviation can't simply be applied to CTR alone, can it? As QS is more than just good CTR.
What else is there to measure?

CTR is 60 to 70% of Adwords QS, let's split down middle and say it's 65%. Another 20 to 25% is keyword relevancy. As far as I can tell, you either are relevant or you're not, much like you can't be a little bit pregnant. About another 10% is other stuff, the big one Google has advertised is page loading time.

While I'm probably over-simplifying (there's very likely more behind the scenes than what I explained), those are the basics. Mainly, there's really only one measure of quality and that is what the searchers are telling you by the CTR. Since you need numbers, a metric to compare advertisers, I can't think of a better way to do this than SD. So, QS is good CTR.

 Originally Posted by thetruth23 Also, my CTR for the last 7 days has gone down by almost 250%. Doesn't quality score get re-evaluated? I would have expected a drop since the historic CTR is clearly much better than this.
Yes, QS will get re-evaluated. Google claims after each search. Keep in mind that the QS you see is not the QS used in the backend. It is not just an integer but a number with many decimals. This means everyone's QS changes, if ever so slightly, for each search.

As I've said, I am simplifying so as to not bring more confusion. Surely Google calculates QS based on many variables such as seasonal. If the history shows a drop in CTR at this time of year, everyone's QS will be re-evaluated based on that. It's very likely not the all-time historical average, it may be the average of the last week or month or the last 100,000 searches. There are so many ways to normalize the data. Your job is not to figure out how they do it, just remember that CTR is the driver and that you want to increase it.
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