Google is to roll out Campaign Drafts and Experiments to help AdWords users test changes and apply the best.
Drafts lets users prep and review multiple changes to current campaigns before implementation.
Experiments is to allow changes to campaigns to be tested.
All these can be measured through the reporting scorecard, or through ad group level.
"Campaign drafts and experiments is currently available for Search and Search Network with Display Select campaigns in AdWords."Google AdWords to Roll Out Campaign Drafts and Experiments