The report's data is calculated by estimating the frequency of your ads from a sample group and then applying it to a full set of impressions to determine their estimated reach. Additionally, the report includes a new metric we call cost-per-head. The cost-per-head is the average cost for you to reach an individual user.
To run a Reach and Frequency Performance report, just head over to the Create Report page in the Report Center. One thing to note is that the report is currently only available for site-targeted campaigns created after January 1, 2007.
