Watson Assistant has some built in analytics, please see the Watson assistant documentation; Metrics overview
If that does not give you the detail you require, you can make use of the Watson Assistant API's to extract some or all of the stored logs; please see the following api doc's - List log events in a workspace
Note: Depending on the level of Watson Assistant you using will determine the length of time the user logs are kept by IBM for. So you may wish to use the api to download the logs into a spreadsheet, or other storage to allow analytics over a longer time period. You can also filter the logs to only bring back certain details, again see the doc's on how to do this.
Finally you can put into your dialog hidden flags within the json payload, i.e. within the context, or output elements (not message part). These flags will then be part of the log, and can be used within your analytics, i.e. a flag for how many times a user answered yes.