Almost all successful films last quite long, on average 140 minutes. In general Oscar-winning movies have been released in the period September-December and they never have a classical happy ending. Music also plays an important role. Furthermore other film prizes are a good predictor for going home with the golden statuette.
If the runtime of the movie was the only significant predictor for the best picture, then Boyhood definitely would have won.
Although the release date of Birdman was also not in line with the historical pattern, one other factor was: the number of awards. Prior to the Academy Award for best picture, Birdman received several trophies for production design, costumes, music, makeup and original screenplay.
Of course, numbers alone can’t predict the Academy Awards and to be honest, although I’m a data scientist I’m glad that not everything in life can be predicted.