Movie studios use market research to reduce their risk of losses by hiring firms such as the National Research Group to conduct test screenings and tracking studies. Often, 300 to 400 prospective moviegoers are recruited to attend a "sneak preview" of a film before its release. After viewing the movie, the audience completes a survey to a. evaluate the quality of directing and producing.b. critique the title, plot, and characters.c. rate the performances of the individual actors and actresses.d. recall specific details of the plot and dialogue.e. compare the final film with the original script.

Obviously the movie is almost finished when these prospective moviegoers attend an sneak preview, so the studios can only change a little of the movie depending on the reviews.

That is why they seek information on the title, plot and characters.

The title can be modified (it will cost extra money), but if necessary, it is something that can be done. A famous example is "The Return of the Jedi" whose original name was the "The Revenge of the Jedi".

The plot and the characters are things that can change a little by reediting the movie. Let's use Star Wars again as an example, George Lucas deleted characters from Episode III at the last moment because they weren't appropriate for young audiences. Again this is an expensive process digitally done.

Very few times the regular moviegoers get to see the full movie, sometimes the full movie is released later including the parts that were cut during editing, Avengers End Game added 30 extra minutes a few months after the release.