Final answer:
It cannot be determined without specific data whether R-rated movies have significantly different running times than PG or PG-13 movies since running time is influenced more by the story and genre rather than the content rating.
Step-by-step explanation:
The running times of R-rated movies can differ from those rated PG or PG-13, but not necessarily due to the rating itself. The rating, which is assigned by the Motion Picture Association of America (MPAA), indicates the appropriateness of the film's content for different age groups rather than the length of the film. Movies rated 'G' or 'PG' are often aimed at younger audiences and can include animated films, while 'PG-13', 'R', and 'NC-17' ratings suggest content more suitable for older viewers. However, the running time of a movie is more influenced by the story it tells and the genre it belongs to rather than its rating. Therefore, without specific data on running times for different ratings, it can not be confidently determined if R-rated movies have running times that differ greatly from PG or PG-13 movies.