Is there an optimal number of partner institutions or partner countries in a PIRE?
This will vary with the project. The existing PIRE projects vary widely in the number of partners and countries involved (see PIRE homepage for webpages and abstracts for many existing PIRE projects). PIs are advised to put together teams that work best for the project they propose, keeping in mind NSF’s interest in funding focused research projects (rather than collections of loosely-related activities) that include well-integrated education programs and strong management plans.