As far as practicable, the tests used in the experiments de 
scribed in this book are given here, together with the instruc 
tions governing their use. Mechanical tests and other non-paper 
tests can be represented only by a verbal description. Many of 
these are described in the body of the book and these descrip 
tions will be referred to. 
It must be borne in mind that minor improvements in the 
character and use of these tests are constantly being made. 
Consequently, in compiling this Appendix for publication, there 
will be points at which it will be slightly at variance with the 
procedure described in the body of the book. 
The arrangement of this material is based on manuals actu 
ally used in giving tests to incoming applicants. It is therefore 
as practical as constant use and experience have been able to 
make it. Tests are listed in numerical order. (No classifica 
tion of tests according to mental faculties is given, because it 
has been found that such a classification has little practical 
value, besides being theoretically unsound.) Numbers are 
given to the tests in order to do away with the clumsy practice 
of recording each test by its full name. Tests are therefore 
usually referred to by number. 
The system used in the application of these tests is the unit 
system. That is, instead of printing a set of tests in a single 
folder for a single purpose—for example, a clerical series or an 
inspectors’ series—each test has been preserved as a unit. Each 
unit can then be combined with other units in any series and 
for any purpose. This method has been found necessary from 
an economical point of view as well as for the sake of greater 
flexibility and accuracy in meeting the highly specialized de 
mands of employment. 
393