Good marketers know that their opinion on a particular color or design or choice of wording doesn’t matter. What matters is how the market responds. So marketers like to test things.

Which headline works best? Does a starburst announcing a risk-free trial help or hurt response? Is it better to offer a special report as a premium, or just keep the page and the offer simple?

That’s all well and good, and those are good things to test. But as you get into testing you have to keep your eye on testing insanity. You start to see other things you can test, …

• Does my e-mail traffic respond differently than my Adwords traffic?
• Do people respond differently on the weekend than during the week? (I’ve suspected this on some of my tests.)
• Do people respond differently during office hours?

The more you test the more variables you see. Sometimes it seems like you could go crazy coming up with new things to test.

I’ve asked Google to change its website optimizer tool so that you can see results during a given timeframe — so, for example, I could see if my weekend traffic performs differently than my weekday traffic.

But sometimes I’m glad it’s not possible to test these things. If you can keep your tests simple, you avoid testing insanity.