Understanding Web Analytics Accuracy – Whitepaper
Metrics understanding, Privacy and Accuracy April 23rd, 2010
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.
If you have further suggestions, or just want to let me know if it was use, please add your comments below. A retweet is always much appreciated |
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(5 votes, average: 4.80 out of 5)



April 26th, 2010 at 5:45 pm
Great Whitepaper! I have already printed out 20 copies and plan on giving them to clients that get “hung up” on why their website analytics data isn’t 100% accurate. Thanks for continuing to create these valuable white papers Brian!
April 26th, 2010 at 6:20 pm
Hello Brian, Glad to see the update version of this super white paper. I’ll read it carefully to check my own comprehension of web analytics data. Just a small notice: I’m reading the P5/19, the page tagging and logfile comparison table. Maybe something is not well placed on the table. Can you check this please? Thanks.
April 27th, 2010 at 12:00 pm
Thanks to Per Strid and Hailong (Scyan) for pointing out that Table 1 was mixed – the cells were labelled the wrong way round. Fixed now.
June 7th, 2010 at 9:28 pm
My manager just sent me your whitepaper and I’m finding it really useful, particularly in understanding where people can fall prey to the data. I work at Compete.com doing much of their support and training so it can be difficult to understand where some of these misconceptions are coming from. Thanks for writing this, it’s a great resource!
August 16th, 2010 at 4:56 am
Hi Brian, would I be right in saying a lot of this is also in the latest version of Advanced Web Metrics?
cheers
Jon
August 16th, 2010 at 1:38 pm
Jon: Yes – essentially it is Chapter 2 from the book, though as a whitepaper I can keep it more up to date with the latest research/thinking.