I believe that Chief was suffering from a Conversion disorder. Due to problems during his childhood due to his father's alcoholism, he shut himself off, and quit talking to people. Not just being a quiet person; he fooled people into thinking he was deaf and dumb.

Some common words found in the essay are:
Randall McMurphy, Maybe I'm, Billy Bibbit, mental hospital, didn't belong mental, belong mental, belong mental hospital, don't wrong, didn't belong, deaf dumb, anxiety disorder, father's alcoholism, mental institute,
Approximate Word count = 493
Approximate Pages = 2 (250 words per page double spaced)