THE  SCOPE  OF  PSYCHOLOGICAL  TESTS  209
select  tests  which  are  appropriate;  (2)  a  preliminary  experiment ­
  with  a  large  group  of  workers  engaged  in  the
same  kind  of  work  in  order  to  determine  the  value  of  the
tests  selected  and  the  standards  which  shall  be  used;
(3)  an  objective  or  impersonal  measure  of  the  work  done
by  the  members  of  the  group  in  order  to  provide  a  reliable
and  accurate  basis  upon  which  to  compare  both  the  individuals ­
  and  their  performances  in  the  tests.  The  difficulty ­
  of  meeting  these  three  conditions  makes  it  impossible
to  apply  tests  intelligently  to  executives  in  the  higher
and  more  specialized  positions.  However,  there  is  a  vast
and  ever  growing  field  where  these  conditions  exist  and
■where  tests  may  therefore  be  readily  applied,  and  some
indications  of  the  scope  of  this  field  have  been  given  in  the
previous  chapters.
With  regard  to  the  qualitative  scope  of  tests,  or  their
degree  of  reliability,  it  has  been  seen  that  their  chief  value
lies  in  detecting  the  innate  or  acquired  mental  ability  of
the  individual.  Tests  do  not  reveal  the  moral  qualities
and  in  this  sense  their  value  is  limited.  But  even  with
this  limitation,  they  make  it  possible  to  select  the  man
who  is  most  likely  to  possess  them.  For,  as  has  been  seen,
the  moral  traits  are  relative,  and  depend  in  large  measure
upon  the  ability  of  an  individual  to  make  good;  and  this
ability  does  come  within  the  scope  of  tests  to  determine.
Finally,  the  knowledge  which  tests  can  give  us  about  the
abilities  of  individuals  offers,  for  the  first  time,  a  scientific
or  objective  basis  upon  which  to  use  the  powerful  stimulus
of  suggestion.  By  the  use  of  suggestion,  much  can  be  done
to  arouse  and  to  create  the  moral  qualities  which  are  desirable ­
  in  a  worker  and  which  will  make  the  worker  not
only  more  valuable  to  the  industry  but  to  himself.