Statistical Analysis: Formula for AdWords A/B testing

This is a really great post on how to use a simple statistical formula to analyze whether your AdWords (or any other) A/B test results are significant and indicate a relevant result.

a smart bear blog [link]

For reference, the important bits:

Define N as “the number of trials.”
For Hammy this is 8+4 = 12.
For the AdWords example this is 32+19 = 51.
Define D as “half the difference between the ‘winner’ and the ‘loser’.”
For Hammy this is (8-4) ÷ 2 = 2.
For AdWords this is (32-19) ÷ 2 = 6.5.
The test result is statistically significant if D2 is bigger than N.
For Hammy, D2 is 4, which is not bigger than 12, so it is not significant.
For AdWords, D2 is 42.25, which is not bigger than 51, so it is not significant.

(Hat tip to Joe Hohertz for the link!)