Increasing the response rate to a mailed questionnaire by including more stamps on the return envelope: a cotwin control study.
Twins taking part in two unrelated studies were sent a questionnaire together with a self-addressed envelope that either carried one or multiple (up to 5) stamps to the same value. The unprompted proportion of questionnaires returned (before commencement of telephone reminder calls) was increased from 62% to 71% in one study, and from 43% to 52% in the other study (test for common odds ratio in studies, p = 0.04).
Duffy
D L
DL
Queensland Institute of Medical Research, Post Office, Royal Brisbane Hospital, Brisbane, QLD 4029, Australia. davidD@qimr.edu.au
Martin
N G
NG
D006801:Humans; D010678:Philately; D012044:Regression Analysis; D017010:Reminder Systems; D011795:Surveys and Questionnaires / Q000191:economics / Q000706:statistics & numerical data*; D013689:Telephone; D014427:Twins