In Custom Reports, what must metrics and dimensions share in order to report accurately?
- Same scope
- Same index
- Same Custom Report
- Same view
Not every metric can be combined with every dimension. Each dimension and metric has a scope: user-level, session-level, or hit-level. In most cases, it only makes sense to combine dimensions and metrics that share the same scope.
Read more here: https://support.google.com/analytics/answer/1033861