I wouldn't base any statistics on IMDB ratings, they're garbage.
Just look at how many awful amateurish experiments there receive spectacular 10 star reviews within days of their release, very likely by cast and crew friends/relatives (or worse), then are buried by 1 star reviews when actual viewers eventually watch them.
Do you maybe have an example? I'm always astounded how well the IMDB score matches how likeable a film is (minus personal preferences of course). 5 is basically always really bad unless I'm a fan of a specific actor/director/genre. The comments are mixed, the comments below the YouTube trailers tend to be quite on point though to see if a film is worth watching