N in n
The 'experiment' group
These nouns are used to describe an action or attempt.
The experiment in democracy was short-lived.
In the case of exercise, lesson, and object lesson, the preposition in is sometimes followed by an '-ing' clause.
This has been an exercise in choosing between lesser evils to limit the damage such cuts inevitably cause.
In the case of lesson and object lesson, the preposition in is sometimes followed by a wh-clause.
essay exercise experiment lesson object lesson
The report describes the campaign as 'an object lesson in how to make the worst possible use of our assets'.