Experiment not showing to all the traffic
I've started using Optimizely about a month ago and have already set up a couple of experiments. One problem that I have noticed across all the experiments is that they do not seem to be shown to all the site visitors even though I allocate traffic to 100% and split it 50-50 between two variations.
The reason that makes me think that is because the number of visitors who see an experiment on a certain page is always lower than the traffic I see on GA on the same page/date range/audience. Let's say I run an experiment and Desktop only - the number of Desktop users that actually see an experiment is at least half of the total traffic that this page gets. I know Optimizely might count visits in a slightly different way, but it can't be that dramatic!
Can it be something with URL trageting match? Does it make a difference if I use Simple match vs. Substring match if I only run an experiment on one page which might sometimes contain different query strings?
Since I am quite new to Optimizely, I'm sure I might be missing something! If anyone had similar problems or has an idea where to start troubleshooting, I would love to hear from you.