APPENDIX  435
For  each  trial  the  exact  time,  number  of  balls  successfully
dropped,  and  the  R.  P.  M.  should  be  recorded.
Rating:  Point  of  reference  for  trial  a  is  60  successful  attempts;
b,  70;  c,  50.  In  each  case,  the  time  is  120  seconds.  Sample
record,  91:  a  —  50;  b  —  64;  c  —  47.  Formula  I  is  applied
to  each  record  separately.  In  this  case,  the  formula  would
work  out  as  follows:  —  =  .82;  —  =  .91;  —  =  .94.
60  J  70  50  ^
Standards:  Only  approximate  standards  for  this  test  have  been
developed.  For  the  type  of  work  described  in  Chapter  X
a  minimum  of  .80  for  fast  machine  operators,  and  .60  for
slow  machine  operators  was  required.