Count into table based on specific choice

Hello,

One table with many courses

One table with many persons

The tables are linked so i can see a list of persons for each courses

I want to include into the course a formula to calculate how many persons are included but with a specific status (choice field).

With this formula cnt(persons.'Name') i get the the number of all the persons included into the courses.

Which formula do i need to use to get only the persons with status (choice field = 1 for example)?

Thanks in advance for your help and have a nice day.

David W.