There were a number of questions and comments on yesterday’s post “conversion testing – how many actions?” and I wish I could respond to all of them.
Instead, I want to offer a practical alternative which plenty of people will take issue with, but I think it’s an important insight to put this all in perspective.
You see, in the early phase of a campaign, I certainly don’t wait for 100 actions. I rarely even wait for 30. Instead, (and this is only possible because I’m always involved in researching the market above and beyond adwords), if I see an ad pulling ahead THAT MAKES SENSE IN THE CONTEXT OF MY UNDERSTANDING OF THE MARKET … I’ll just go for it after 10 or 12 clicks. (There, I said it and lightening didn’t strike!)
This is INCREDIBLY RISKY from a purely statistical perspective, yet on a day to day basis I can get traffic flowing in a new market MUCH quicker than waiting for a 95% confidence level (e.g. 100 actions, or even 30). Moreover, my understanding of the market moves forward fast.
Do I accidentally delete winners when I do this? Yes, absolutely, positively, and definitely. (So use at your own risk)
But the time and money spent on the experiment is downgraded and I can move at the speed of the market. You see, the time and money you allocate to a test are ALSO a risk… leaving a test up too long has it’s costs too.
I start paying careful attention to statistical probabilities AFTER I’ve got something worth protecting (a “control worth beating”). The more it’s worth, the more successful history the ad has, the more protective I am, and the higher level of statistical confidence (or greater number of actions) I’ll require.
So my personal interpretation of Google’s recommended 100 actions is that WHEN YOU’VE GOT A CONTROL WORTH PROTECTING, what we previously thought was enough actions really isn’t, given the “noise” on the internet. (“Noise” = number of advertisers coming in and out of the market, changes in the economic news which are instantly available online, varying ad position and impression levels, changes in the organic rankings, public events, … even such things as internet worms and viruses which affect browsing behavior)
Bottom line?
When you’ve got something already making money, it might pay to wait longer than we’ve all traditionally thought. How much longer? Probably twice as long as you think.
But ultimately it depends upon how much you’re making, how much you already know about your market, and how big a bridge you’d jump off if you accidentally killed the winning ad 
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