Details of these implementations can be found here and here on Simo Ahava’s blog.
Once implemented, there are just a few more steps left. Depending on the site’s goals, we need to come up with thresholds that will mark a visit as “nonbounce.” These thresholds will define activity levels that will separate a bounced visit from others. For some of the sites, we have opted for 25% scroll and 15 seconds time on page as markers of a nonaccidental visit. A visit with that level of interaction with the page will be marked as a nonbounce visit. This is done using the confusingly named “Non-Interaction Hit” field in GTM. Once again, here’s Simo with the best possible explanation of this implementation.