Why do my stats look different?
By Benj Arriola - Posted on Wed Feb 21, 2007Web statistics, web analytics, whatever you call it, what ever you use, Webalizer, AWStats, Analog Stats, SiteMeter, Google Analytics, Webtrends, WebsiteStory, Enquisite, Omniture and all these other visitor tracking number software may sometimes present different results. Maybe with small differences, could be neglible, but sometimes these could give significant differences that are large enough to doubt the validity of these generated data.
A common difference among these softwares can be based on how they acquire data. These are usually done in two ways:
- Reading Raw Session Logs generated on the server
- Javascript tagging and use of cookies by adding a small peice of code on every page you wish to monitor.
These two methods could give you two different results.
- On IP Addresses: Unique visits using raw session logs read IP addresses, Javascript tagging with cookies read browser cookies.
A corporate ISP account can have many hits from many people, but in session logs, only 1 unique hit is recorded since the corporate account could be all on one IP, while tagging and using cookies will treat each browser hit on a different computer as separate unique hit. - On Cookies: People that do not accept cookies and/or clear cookies will treat two separate visits from the same person on the same computer as two unique hits. Although most Javascript tagging softwares, if cookies are cleared, will move back to IP addresses. In some cases, if cookies are cleared, referer logs may not be detected well and considered to be direct hits.
- Proxy Servers: ISPs with proxy servers will not fetch websites from the servers source. This a hit will no be counted on raw server logs. Although Javascript tags are in the website’s source code and will run everytime the page is loaded.
- Partial page loads: On an uncompelted page, raw server logs are already recorded, but not exactly true with Javascript tagging where most of the time it is recommeded that the Javascript tag should be placed just before the closing </body> tag. In that way, we are sure that the visit to the page loaded a complete page before it is recorded as a valid hit.
So when looking at the numbers, note that there may be even more issues for differences in results and no single web analytics software will get it 100% correct.
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