Now, let's say you have 10 websites with same ad size and placement. It'd be good to put 10 different channels to see how each ones doing. But what if you put the same "channel ad in all the 10 websites. Wouldn't your impressions go up, so your CTR/CPC goes up along with it? If any Adsense experts out there who has tried this, any advice would be appreciated.
I'm not an expert, but I prefer to create an unique channel to each combination of website + placement. It helps me when I need generate a new report: I can identify which channels I want in one report looking their names and if I select all channels I'll have 100% of values (that's, correct values), not 130% or 200%. One of my friends used same channels in differente placements (each channels was one keyword) and confused himself when he needed generate new reports.
You can do that. I usually channelize sites of the similar niche under the same channel and sell them together. But the correct CTR can't be accurate if your themes are different.
if you put the same channel on 10 sites, your impression showing on that channel will be combined impression from all 10 sites and you will not know which site had how many impression, clicks, and made how much. its wise to use seperate channels
Yes, I know you can put it in different channels but can you make more money by putting them in the same? (is the question)
Yes, the question is, does CTR/CPC depend on the "channel" or "website"? If it depends on "channel", it does make quite a sense to put multiple sites in 1 channel as your base CTR/CPC goes up when you have certain number of impressions. (e.g. You start a new website with 100 impressions and get 1 click, there's a good chance your CPC is very very slow whereas if you have a website with 10,000 impressions, your CPC is higher. Now what if you put 1000 of those small websites with 100 impressions together in 1 channel?)
The answer is no. The only thing that changes is the presentation of the data. Using a unique channel for every single ad place or experiment would give you the most precise data. However, that will take up all your channels availabe real quick depending on how many sites and/or channels you have. I use a 3 letter code to begin every channel: APA_Top Right Block That channel might include 10 different sites using that same ad identically. This way I can tell how an ad is doing, efficiently, across many sites.