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In 40+ years as a student and practitioner of copywriting, I’ve often come across the advice to only test one variable. But some people might be taking that too far. In my email recently, I saw someone assert that the variable has to be tiny, like changing a single word in a headline.
You might remember that I most recently discussed the difference between Kaizen (continuous improvement, usually through small steps) technology improvements and technological Great Leaps in my October newsletter. Just like any other culture change, I think copywriting changes can be Kaizen—or they can be Great Leaps.
Let’s say there was such a thing as a haircutting robot, and you’re a copywriter assigned to write headlines for that device. Sure, you can test a single-word Kaizen variable like New Instant Salon Cuts Your Hair While You Sleep vs. This Instant Salon Cuts Your Hair While You Sleep–but I think it’s also fine to test a big-leap variable like New Instant Salon Cuts Your Hair While You Sleep vs. Wake Up Tomorrow Morning with the Hairstyle of Your Dreams.
I’ve always understood the one-variable rule to mean that if you’re testing the headline, don’t change the body copy, the layout, etc. in the same test. But the change could be as small or as bold as you want.
And why not test three or even four headlines in an A/B/C or A/B/C/D test? As long as it’s emailed to the same demographics and the same list on the same day, we can track a lot more things now than we could in the old days, so why not? We can even test for things like how response translates into long-term customer value. One version may get more clicks but fewer buys or lower total purchases. Make sure your testing gives you the metrics you need to properly evaluate your efforts.
By the way, I’d argue that there may be good reasons to violate the one-change rule, and strategies for understanding the data when you do. As an example, if you’re dealing with a time-sensitive offer that’s going to be worthless in a month, you may want to test a whole lot of stuff all at once. Go ahead, call me a marketing heretic!
And if you want a heretic’s fresh thinking in YOUR marketing, especially if your firm makes a positive difference in the world call me: 413-586-2388 (8 a.m. to 10 p.m. US Eastern Time—or email me with the subject, Your Marketing Services—Newsletter Reader. (Note that I’ll be away with very limited email through August 22. I recommend writing your email right away but scheduling it to arrive a few days after I get back.)
