It’s a very, very, bad idea to attach handlers to the window scroll event.
Learn to track page performance, user behaviors, personas and more with the power of GA Custom Dimensions.
Creating audience segments is one of the most important things you can do with an analytics tool. When segmentation rules do a good job of highlighting motivations of visitors, behaviors of each segment help make sites become more relevant to each group. This will increase the likelihood that your site will deliver on your goals.