Since the standard Google Analytics platform is offered at no cost, Google only offers so much processing power and limits the amount of data that is allowed for each view in a Google Analytics account. If your website has a large amount of sessions, you may notice a yellow box at the top right of the report stating that “this reports is based off of x% of total sessions.”
Sampling in Google Analytics is important to Google; the complex queries of dimensions, metrics, and segmentation across potentially millions of sessions that are contained within Google Analytics are very computation intensive. In order to throttle the legwork that the service provides without limiting users ability to analyze overall trends, Google uses sampling.Read More