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Inconsistent Visitor Numbers

andrew_waite 11-24-14

Inconsistent Visitor Numbers

Hi There,


Im running a URL redirect test. Im tracking page views (simple match) 


My question relates to traffic numbers - analytics has me numbers for the experiment period well above 2000 - however optimizely has only recorded around 700 unique visitors.. Can anyone sheed light on why this is? 


adzeds 11-25-14

Re: Inconsistent Visitor Numbers

It is difficult to get a good understanding of these sorts of issues from a distance as there are a number of factors that could cause this.

I should point out as well that I have never had a test that correlated 100% with my analytics data, there is always a certain % difference.

Some things to look at would be the location of the scripts on the page, is Optimizely at the top and GA at the bottom? They might be running at different points and sometimes one or the other is not getting run.

Do you have an audience defined in Optimizely? Is this restricting the number of visitors that would see your test?
David Shaw
Level 11
siherron 11-25-14

Re: Inconsistent Visitor Numbers

Hi Andrew_Waite,


As a start point it is worth remembering that Optimizely uses a 10 year cookie to measure visits/visitors and most other forms of analytics tools use a mix of session cookies and 1x1 pixels. This leads to discrepancy between visitor measurement across tools.


These articles might help:



As a rule, when a test is running, I tend to only use measurement data from one source (Site Cat, GA, WebTrends, etc) OR Optimizely as I want to be confident that the story is consistent.


I hope this helps? 


Simon Herron
Optimisation Consultant
Level 2