With so much integration of tools to so many content management systems, we're seeing many more of our clients having issues with Google Analytics scripts being inserted into the page multiple times. This wreaks havoc on your analytics, resulting in huge over-reporting of visitors, pages per visit and nearly no bounce rate.
Just today we had a client who had 2 plugins loaded and configured to add the Google Analytics script to their blog. And neither plugin actually checked to see if there was already a script loaded! The result was that the visits were over-reported and their bounce rate was about 3%. If your bounce rate drops to under 5%, rest assured you have an issue with multiple scripts on your page.
Aside from Analytics, how can you tell if you've done this? One method is simply to view the source of your page and search for ga.js. Even if you want to monitor the site with multiple Google Analytics accounts, there should be only one script.
Another way is to open up your developer tools in your browser and view the network communication after you refresh the page. Do you see the ga.js script being requested more than once?
Google Analytics works by loading a script that assembles all the information, saves the information to browser cookies and sends it to Google's servers through an image request. When the script is loaded more than once, it sometimes overwrites cookies, and sends multiple image requests to the server. That's why the bounce rate is so low… if you visit more than one page on a site, you do not bounce. So… if the scripts are firing more than once when you visit a single page, it means you've visited multiple pages.
Check your page and your analytics to make sure your analytics script is properly installed on your site, and make sure you don't accidentally load the script more than once. If you do, your data is not accurate.