Unices and applications use the setgid and setuid bits so the octal may need to be 4 digits, especially if using UniCenter or AIX. AIX directories often have setgid set sometimes.
Using chmod 0755 or 0750 if hardening is needed. remove setgid from dir with symbolic representaion drwxrws--- ie in octal 2750 change to safer nonsetgid drwxrwx--- ie in octal 0750 with chmod 0750 dirname
Usual ownership requirements apply. Note it is possible to get uppercase S appearing in ls -l output if setgid is set but no execute permissions are set. it means setgid is ineffective.