INSTRUMENTS FOR CHECK READING 



93 



the task of checking them. Such layouts 

 might employ circular scale instruments, 

 each with its scale starting point so chosen 

 that the null or desired indication on every 

 instrument is in the same position — say at 

 the 12 o'clock spot. They might also em- 

 ploy thermometer-type, vertical indicators 



inches in diameter, arranged in a 4 x 4 

 square pattern. When the panel was ex- 

 posed, the subject, responding by voice and 

 switch operation, indicated whether all the 

 dials were set in a prescribed manner or 

 whether one or more of them was off. If the 

 latter was the case, the subjects were re- 



TABLE II 



Some Typical Results on the Accuracy of Scale Reading 



UNDER Different Experimental Conditions 



all nulUng at the same height, or a simple 

 set of pilot hght, "all or none" indicators. 



A test of the relative merits of different 

 ways of arranging dial type instruments for 

 check reading was recently reported by War- 

 rick and Grether (82). They used an instru- 

 ment panel containing sixteen dials 1.75 



quired in some tests to report the direction 

 of deviation from the desired setting, i.e., 

 too much or too little. It was not difficult 

 for Warrick and Grether to show that a plan 

 of aligning the null positions for all instru- 

 ments is superior to having the check posi- 

 tions differently located on different instru- 



