Paired t-tests are a form of blocking, and have greater power than unpaired tests when the paired units are similar with respect to noise factors that are independent of membership in the two groups being compared.
The service, by the way, is called AOL My eAddress. AOL says it supports .com or .net domains, up to 100 e-mail identities per domain, 2 GB of storage, spam filtering, and open mail clients such as Outlook and Thunderbird through the IMAP protocol.
And ... AOL owns a lot of content brands, such as Techcrunch and Huffington Post, that publish a lot of video. AOL CEO Tim Armstrong has for years been pursuing the idea that he might somehow turn AOL into a sort of internet-based cable TV competitor. And AOL as an advertising seller has been succeeding of late â revenues grew 7.2% in the most recent quarter.