The Math Behind the 20 Pairs Nofollow Test So then why don't

[zihadhasan019]

We run this as our next test? The answer is simple. A 168 trials is a lot of domains to setup. So maybe we will get lucky. If we do a good job of controlling for other factors, and the nofollow sculpting has a modest effect, perhaps the nofollow will win much more frequently than 62.5% of the time on average. To see a 95% significance of nofollow doing better than the control, we will need to see 15 wins for nofollow out of the 20 trials.


One could do more math for this, but how we actu australia business email lists ally got this number was an online binomial distribution probability calculator. Plug in p=0.5 (as this is the null hypothesis), n=20, and many various values for the numbers of wins until you find the lowest number whose chance of getting greater to or equal to it is less than 5%. That number should be should get 15. Is there any takeaway from the original test? Thousands of people read the post about the first PageRank sculpting methods and based on my assessment took it as truth.





It wasn't until two days after posting the original entry that Darren Slatten pointed out my mistake. That means that the damage had already been done and it would be practically impossible to contact all of the people who had read the post. The small amount of people who did notice were (rightfully) upset with me. Their frustration with me and SEOmoz was vented on their personal blogs, Twitter, Facebook, e-mails and in the comments on the original post.