The following is a designed experiment. Identify the type of design, treatments, observational units, and experimental units.
You and a friend have two different procedures for making paper airplane. You want to compete and see who has the airplane that is easiest to make and can fly longest. You pick 10 of your mutual friends (who have different, inherent capabilities when it comes to making paper airplanes) and ask each of them to recreate the airplanes. That is, you provide each of them two pieces of paper and randomly assign which piece of paper is employed to make one of the airplanes.