We all know the horrible sign in Google Analytics that looks like this:
You want to analyze a bunch of data but because of that sign you know it will be sampled (incomplete) data. So, what is "sampling" exactly and how can you prevent it.
What is sampling
After Google Analytics gathered the raw unaggregated data that is being tracked by the tracking script it processes it to understandable and useful visit data. And with that visit data all available standard reports are pre-calculated and stored. That means for example that if you try to get the "Top Content" report, Google Analytics can show it to you in seconds because most of the calculations are already done.
Often I get questions about how you can tell if a Google Analytics implementation is successful. People don't want to wait at least 4 to in some cases 24 hours before they see some data... or not. That's why I will tell you how I check this seconds after the codes are placed.
How does the tracking work
Google Analytics uses pixel tracking technology to send data to the Google servers. That means that the GATC (Google Analytics Tracking Script) will put a little image on the page that is being tracked. The URL of this image looks like this: