Power Direct Marketing: The Book
The Square Root of Wonderful
And then there is another. The Square Root of Wonderful. Which is a little different from the others.
Just because one list or offer pulls a few more responses than another doesn’t always mean it is actually better. Remember, you’re testing samples of a universe and measuring what happens. Analyzing to determine the next best step to take.
Sometimes the difference between 2 lists is simply the sample size. Sometimes it is more complex, with one offer dramatically different than another. A price test is a good example—where you are measuring the effect on response of one price, $29.95, against another, $49.95.
There are all sorts of mathematical tables and formulas to figure all this out. But, if you’re like me and had trouble with high school geometry and introductory algebra, you’ll appreciate the Square Root of Wonderful. It goes like this:
If the difference between 2 tests is greater than the square root of their total, the difference is statistically significant. And you should pay attention to that difference.
Example 1
- Package "A" gets 38 responses
- Package "B" gets 62 responses
"B" – "A" = 24
The square root of "A" + "B" =
the square root of 100, or 10. Since
24 is greater than 10, the difference
here is significant.
Example 2
- Package "A" gets 54 responses
- Package "B" gets 46 responses
"A" – "B" = 8
The square root of "A" + "B" =
the square root of 100, or 10. The
difference between these two
packages is too close to call—they
are statistically identical.