oo EMPLOYMENT PSYCHOLOGY 
ingenuity of the more successful direct-mail copy-writers is 
needed to insure a maximum proportion of replies. Ques- 
tionnaires to be sent by mail should be exceptionally brief 
and should be accompanied by a tactful letter explaining the 
nature of the inquiry and the service which can be done the 
applicant by giving correct and conscientious answers. The 
same letter may enclose a rating scale. An example of such 
a letter and rating scale is given in Figures 17 and 18. 
It pays to follow up an inquiry. Toops (203a¢) made a 
careful study of questionnaires sent out to graduates of a 
trade school, to determine the success of the instruction. 
By the use of five follow-up letters in addition to the one 
originally sent with the questionnaire, he succeeded in ob- 
taining completed questionnaires from 93% of the graduates 
whom he was able to reach by mail. The cost per reply 
from the first letter was $2.77; the final cost per reply of all 
returns was 68 cents. Among the most important points 
he makes are the following: There was no great difference 
between the data from those who replied at once and from 
those who required a large number of follow-up letters to 
arouse them to reply; in other words, those who reply 
readily are not a biased sampling. The shorter the ques- 
tionnaire the better are the chances of getting replies. The 
cost per return will be decreased by continuing to send 
follow-up letters until practically all the questionnaires are 
returned. When the curve of cumulative returns from a 
mail canvass becomes almost horizontal, it is time for an- 
other follow-up letter. The week-end holiday is the time 
when recipients are most likely to fill out questionnaires, and 
mail should reach them toward the end of the week. The 
letters which Toops used, printed in full in his article, will 
suggest ways of wording such letters in order to insure suf- 
ficient replies. 
The telephone is better than the mail in checking the 
worker’s statements and in obtaining information from his 
references. Data may also be obtained by company in- 
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