There is not a set minimum number or percentage of participants that IDI, LLC recommends should complete the IDI in order to get an accurate understanding of an organization's or group's level of intercultural competence. It also depends on what the organization or group is hoping to learn from the IDI data collected.
Because an organization or group is made up of people, to get the most accurate understanding, ideally the IDI would be administered to as many individuals as possible. However, we understand that this is not always possible.
If QAs are interested in getting a "snapshot" of an organization or large group, and opt to administer the IDI to only a sample of the organization, they should think carefully about how they select the individuals who are invited or allowed to participate, and what implications that might have on others in the organization who do not have the same opportunity.
One alternative approach is to start by administering the IDI with all members of leadership teams. This would not be representative of the organization as a whole, but would represent those who likely have the most influence, make policies, etc., and can provide useful information.
QAs may also wish to consult a statistician for guidance on recommended sample sizes, in particular if they are looking to illustrate statistically significant findings. Below are some non-IDI related articles that may be helpful in thinking about sample size.