Paid landing pages generally use noindex. However, if a copy of the homepage is used for paid testing (on a separate url), and a winning variation may then be pushed live to replace the current homepage: should this be treated almost like a test, and a rel-canonical is warranted (to the canonical HP) rather than a noindex? Also to prevent human error when the test version is pushed with noindex still there :)
Selected answers from the Dumb SEO Questions G+ community.
Richard Hearne: If you migrate a winning challenger to the homepage spot then of course you should remove any NOINDEX directive that the page had as a test challenger, and the homepage should always self-canonicalise.
The human error you mention would not be welcome at all, so great care should be taken to avoid that particular misstep.
Yuliana Kronrod: Richard Hearne definitely don`t want that to happen. Do you see any issue with canonicalizing vs noindex for the test HP?
Richard Hearne: Yuliana Kronrod what`s the goal of the test? What hypothesis is being tested here?
Stockbridge Truslow: I agree with Richard - your landing page for the paid search is going to have traffic keyed from only the keywords you`ve bought and nothing else. The traffic is more specifically targeted and may be better or worse qualified than traffic going in organically to the main home page. You can`t learn much that way.
If you really want to see which of two pages is converting better - look up A/B Split Testing and read a bit. There are plenty of tools for most CMS systems that will help you randomly (and evenly) split which page is seen as a landing page. Google Analytics has tools to help you track which one is converting better, too.
It can be a bit daunting when you first look at it because it`s sometimes got a bunch of steps to set up properly - but most tools for most CMS`s will have plenty of walkthroughs, documentation, and even sometimes videos (if that`s your thing) to help you through it.
Yuliana Kronrod: And for more context - split tests of the homepage are being run independently of the paid program, with yet another version of the homepage that’s canonicalized and not noindexed.