Google AdWords experiments can provide insight into increasing click-through rates and conversions.

Running successful long-term AdWords campaigns can be a balancing act between key word selection and budget allocation. Google AdWords experiments provide an avenue to test new ads and keywords against existing ads at the same time. However, there can be a downside to running an experiment in the form of a drop-off in click-through rates (CTR) and conversions while the experiment is running.

Budget allocation and timing are two factors that can affect ad performance during the experiment.

Budget allocation is the first thing to address. When setting up the experiment, by default, Google allocates 50% of the existing daily ad group budget and places it toward bids for the experimental ad. If your campaign is budget challenged in the first place, you are effectively reducing your daily budget by half for the existing ad. If the existing ad has been pulling well in terms of conversions, this will reduce the conversion rate due to less budget.

The comparison factor comes into play when viewing the analytics for the experimental ad. Experimental ads are created to test new campaigns, keywords, ad extensions, and callouts to see how they will affect conversion rates. The data to look at is the click-through rates for the experimental ad as compared to the existing ad. For this reason, allocating somewhere around 30% of the daily ad group budget for the experimental ad will give you a better idea of the effectiveness if the CTR is higher than the existing ad while consuming less of the daily budget.

The other option to consider is increasing the daily budget while the experiment is running so the existing ad continues to pull the necessary conversions based on your bid strategy.

The second factor that affects experimental ad performance is timeframe and time of year. Determining how long to run the experiment is subjective — one week, two weeks, two months — how long is long enough to make a data-driven decision? Depending on the daily ad group budget, time of year, and the product offering, several months could be a reasonable timeframe if you are confronting the holiday season and the product offering is a business service.

Running experiments is a good practice. You may have a core set of effective keywords in terms of impressions and click-through rates; however, there are a multitude of outside factors that can affect ad performance. Prudent AdWords advertisers are always reviewing their analytics to improve conversion performance.