A related measurement is linked to a calculated dimension and used to populate the dimension values in a list. You can add a related measurement when creating a calculated dimension, in the Advanced section.
When a calculated dimension is added to a list, such as to populate an interactive filter widget, the dimension values from the relevant data stream type are pulled from the database.
For example, you're using a calculated dimension based on Campaign Name, and you want to use the dimension in an interactive filter. Unfortunately, you have mutually exclusive campaigns in your Ads and Conversion data. Use a calculated measurement that includes Impressions and Total Conversions as the related measurements. This way, your calculated dimension works for both ad and conversion types, giving you the results you need.
Calculated dimensions can generate values from different data stream types, as long as the related measurements pull measurements from other data stream types.
To use a calculated dimension that includes an entity that exists in multiple data stream types while including all the values of the calculated dimension, create a new calculated measurement. Then use the new calculated measurement as the related measurement. The calculated dimension applies to both data tables and unifies the values into one list.
Selecting a related measurement with no values doesn’t affect the results of the calculated dimension.