No science, no full data but an estimate according to my viewing habits and to how I use trakt:
- When I switched back to a movie during the same TV broadcast I count it as 1 play.
- Movies with the same amount of plays I sorted by their respectively movie length.
- I sorted out 25 movies with 3 plays with at least one clearly not fully play
- I click on "play" when I watch a movie for at least 3 min.