Testing CTR on different ads

November 12, 2005

Source: marketingnewsblog.adwordstraining.org

Author: steveblom

Question: ok - 2 identical ads (and I mean identical), over 1000 impressions spread almost equally across the two ads - one ad gets a ctr of 16.7 and the other 9.7%

explain that, oh guru.

Answer:
Who let the CTRs out?!
Ok here is the deal:

1000 impressions is statistically very small, and the CTR can vary greatly. 10-20,000 impressions is a lot better to judge as far as what the actual CTR is.

In this case, you had two identical ads, and I am assuming you created them and activated them at exactly the same time. If you leave them for longer, they will tend to even out. But there is always a possibility of a software glitch, so if you get to 10,000 impressions and they don’t even out you can always contact customer service.

This reminds me of another good point though. WHEN do you decide what the CTR for an ad really is? I used to think it was 1000 impressions, but now I am finding even more waiting is necessesary before I “pull the plug”.

One time I was real excited because I had two hot ads, one at 10% CTR and the other at 7% CTR, and about 200 impressions each. After they each got 1000 impressions the 7% one had gone down to 3.8 and the 10% one had gone down to 3.2, where they both stayed consistently for a long time. In other words, you don’t really know what the winner is going to be until it is statistically relevant, and the Google system is sometimes much to premature in declaring a winner. http://www.vertster.com/adwords-tool is a good tool I have found for determining the likelihood that you are indeed choosing the correct winner between two ads you are split testing.

Steve

Question:
popular keywords that only have one or two ads

Why have google suddenly started charging so much? I used to be able to buy the keyword ‘plato’ for £0.04. (UK) They now want ten times that. My ad is relevant - I’m selling a book involving Plato, they aren’t filling all the ads, why do they want so much money?

Answer:
Well, basically they are in business to make a profit, and maximize that profit.

The only thing you can do is work on improving your “quality score” by testing different and better ads. You want to get a higher percentage of people who click on your ad, and then you can reduce the price once you get a little traction on those ads.