splitwit

This plugin automatically adds the SplitWit code snippet to your WordPress site. SplitWit lets you create a variation of your web page using our visual editor. It splits traffic between the original version and your variation. You can track key metrics, and let SplitWit determine a winner. No code needed.
After creating a SplitWit account, and starting a project, you can add the project ID code to the plugin’s settings page. That’s all you need to start improving your site’s conversion rate.
This plugin relies on SplitWit, a third-party service. The SplitWit service adds code to your website to run A/B experiments. It also collects data about how users interact with your site, based on the metrics you configure.
SplitWit Terms of Service: https://www.splitwit.com/terms-of-service 
SplitWit Privacy Policy: https://www.splitwit.com/privacy-policy

SplitWit

Optimize your website for maximum convertibility. This plugin lets you use SplitWit to run experiments on your WordPress website.

bhalliburton

peterbessman

This plug-in allows you to enter an alternate headline for every post on your blog. The headlines are then randomly alternated on your website until a certain number of “headline views” has been reached. At that point, a “winning” headline (as determined by the number of people that have clicked on each headline to date) is determined and that headline is shown going forward.

Headline Split Tester

Headline Split Tester allows you to have two competing headlines for blog posts. They are randomly shown until one headline wins.

SplitWit vs Headline Split Tester