AdWords Campaign Experiments, or ACE: a tool that will help you optimize your account by letting you accurately test and measure changes to your keywords, bids, ad groups and placements. As part of our ongoing effort to improve your AdWords experience, we’re testing this new tool and inviting U.S. advertisers to participate in the beta.

In the past, the most common way to measure how changes to your account affected your campaign performance was to measure how the campaign performed before and after you implemented your changes. However, this type of analysis can often be complicated by events that occur during the test period, including holidays, weekends, or changes to end user or advertiser behavior.

ACE allows you to perform faster, more accurate tests by executing your experimental campaign alongside your original campaign. By performing this type of simultaneous split test, we can tell you precisely if your campaign changes produce statistically significant results.

Different ways of using ACE
Use ACE to experiment with any combination of bid, keyword, ad group or placement changes. You can test and measure a variety of scenarios including:

• The incremental impact of adding new keywords to your campaign or changing keyword and ad group-level bids
• The value of restructuring your Content campaigns to use more tightly themed ad groups
• The change in volume by using different keyword match types
• The value of using an ad group default bid versus keyword-level bids
• And much more!

(Source:  Google Adwords)