Illustration of Simpson's paradox:

                      personality disorder w. negative language   no disorder w. negative language
  total                                992    75%                         945    25%

but actually

                      personality disorder w. negative language   no disorder w. negative language
  had a rough time in life             909    80%                          79    80%
  had a decent time                     83    20%                         866    20%

(Figures made up.)