The majority of the plays were written by William Shakespeare solo, and this includes the most well known like "Hamlet", "Romeo and Juliet", "Othello", "King Le

The majority of the plays were written by William Shakespeare solo, and this includes the most well known like "Hamlet", "Romeo and Juliet", "Othello", "King Lear" and so on. But a number of plays were written in collaboration with other playwrights - for example the play "Two Noble Kinsmen" mentioned in the article, which was written in collaboration with John Fletcher. See https://en.wikipedia.org/wiki/William_Shakespeare%27s_collaborations https://en.wikipedia.org/wiki/William_Shakespeare%27s_collab... for other collaborations. Quantitative textual analysis have indeed been used to try to discern which scenes were written by who. The method is still pretty controversial though, and subject to the pitfalls of machine learning - selection of training sets, overfitting and so on. For example new edition from Oxford press attributes Henry VI parts 1-3 to Shakespeare and Christopher Marlowe, but this is highly controversial. The attribution are based on similarities to Marlowe's style, but critics have pointed out it could just be Shakespeare emulating Marlowe. However the theories that all of Shakespeare's plays were written by a committee or by someone not called Shakespeare, are just fringe theories without any serious support.