I first wrote about web analytics accuracy in 2007 while working at Google. At that time numerous clients (big spending Google advertisers my team helped) were contacting their Adwords account managers asking why Google Analytics numbers did not match their AdWords click-through reports, or for that matter, match the other web measurement tools they were using.
These of course are legitimate questions. However there are a multitude of possible answers – not what you want to hear if you are the end-user trying to interpret your visitor reports! The original accuracy whitepaper (published in Feb 2008) explained all of the possible accuracy considerations I could think of at the time. It was a vendor agnostic accuracy check-list to help the end-user, and those that you report to, get comfortable with the data, its limitations and how to mitigate these.
Two years later and things have moved on. Accordingly I have updated the whitepaper to include all my latest thinking and add new data points from other people battling with accuracy – notably at study conducted by Paul Strupp and Garrett Clark at Sun Microsystems. The basic accuracy issues I originally describe haven’t changed – just augmented for April 2010 and now 19 pages…
If you are an agency with clients asking the same accuracy questions, or an in-house marketer/analyst struggling to reconcile data sources, this accuracy whitepaper will help you move forward. Feel free to distribute to clients/stakeholders. As before the whitepaper is vendor agnostic. That is, the principals and issues discussed are relevant for all on-site web analytics tools.
Understanding Web Analytics Accuracy
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