Google Website Optimizer v 1.0 The Techie Guide - Manual (Page 6)

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The Techie Guide to Google Website Optimizer
How Experiments Work
A/B Experiments
For A/B tests, the sequence is almost the same. But instead of GWO replacing pieces of the page content
dynamically, it redirects the visitor to one of the prepared test pages.
The Control Script for an A/B experiment is nearly identical to that of a multivariate experiment. It contains
an extra script that when executed calls the utmx function. The utmx function will either not do anything (if
the user is to see the original) or redirect the user to the B or C pages.
Detailed Explanation of MVT Experiments
Now let’s take a more technical look at what happens for MVT experiments:
1. The visitor’s browser makes a request for http://www.mysite.com/landing_page.html
2. The contents of landing_page.html are loaded into the browser. (Technically the page is streamed to
the browser and the parser won’t see the whole page until after all the data has been streamed in and
the inline scripts executed).
3. The GWO Control Script (at the top of the page) executes.
4. The Control Script looks for a GWO cookie. This is to see if the user has visited the page before.
5. The Control Script makes a request from Google’s servers for an additional script, siteopt.js,
appending the experiment key and GWO cookie values, like this:
http://ww w.google-analytics.com/siteopt.js"position:absolute;top:557px;left:112px;white-space:nowrap" class="ft04">key>&utmx=<__utmx cookie value>&utmxx=<__utmxx cookie
value>&utmxtime=
If this is the visitor’s first visit to the page:
• The utmx and utmxx values passed to siteopt.js will be empty.
• A combination will be randomly chosen for the visitor
• siteopt.js will set the __utmx and __utmxx cookies.
If this is not the visitor’s first visit to the page:
• The utmx and utmxx values passed to siteopt.js will have the values that were previously set.
• The combination chosen for the visitor will be based on the utmx value.
• The GWO cookie’s two-year expiration date is reset.
siteopt.js includes the code that defines the utmx_section function. This is the function that actually replaces
the content on the page.
The utmx_section functions are executed, which replace the content for each section. The content to be
replaced comes from whatever was entered when the experiment was set up.
If the section content to be shown is the original version of the content, GWO will do nothing to that section.
The user will simply be shown the original section content. If you modify the content on your original page
after the test begins, users will then see whatever changes are made.
The visit tracking code runs, which tracks a visit and the combination seen. This is basically a standard
Google Analytics (GA) tracking call, using a custom “virtual URL” representing a visit to the test page.