There are several additions and variances in the movie. First of all, the scene where the children and Tituba are dancing in the forest is never seen in the forest; we simply learn of it from dialogue. This scene was most probably added in the movie for a dramatic effect: foreshadowing.
Along the same lines, there are many scenes included in the movie that are outdoors, however; there were no such scenes in the play. All of the action in the play was indoors. The director, in this case, was simply using the advantages of movie making. It is difficult to replicate an outdoors scene in a theatre. Also, some of the techniques used when filming outdoors create a symbolic message. A portion of the scenes before the beginning of the witchcraft trials is seen in a downpour of rain, possibly foreshadowing doom and dreariness to come.
There were some scenes added or adapted in the movie as opposed to the play. First, the large group of "stricken" girls, which indeed had a greater number than did the group in the play, left the church meeting at the beginning of the movie to see about Betty's condition. Betty seemed to be much more violent in the movie and she tried to jump out of the window, which did not occur in the play. These details were most likely added to augment the idea of "mass hysteria." A scene was added in the movie, showing the hangings and cheers of the crowd watching, also to add to that effect.
Next, Tituba was not whipped into confession in the play, whereas she was in the movie. This was most indefinitely added to show that the profession was typically not made willingly. One had to be forced one way or another into confessing, to save their skin or their life. Also, around the time of this scene is one where Abigail...