interview__diagnostics file is a special service file, automatically produced with every data export, that contains useful information for assessing the quality of interviews:

• number of invalid entities (invalid answers and errors in static texts),
• number of questions with comments,
• duration of the interview etc.

For a description of available fields and their types, refer to this article.

This is especially useful for user-written monitoring systems that work alongside Survey Solutions and continually monitor the quality of incoming data by periodically exporting the data and building customized reports. Supervisors already had access to all the same information interactively through interview details and interview history pages. The interview statistics API endpoint has been updated to obtain the same information for API consumers.

This feature was proposed by Andreas Kutka and other users.