In a randomized study of envelope and ink color, colored ink was found to increase the response rate to a postal questionnaire.
OBJECTIVE
To assess the effect of the colors of the envelope and ink on the response rate to a postal questionnaire in a study screening for undiagnosed parkinsonism in people aged 65 years and over in the community.


METHODS
A total of 2,524 people aged 65 years and over from five general practices in Aberdeen were randomized to receive a questionnaire about the symptoms of parkinsonism printed in either colored (green) or black ink, and sent out in either a brown or white envelope.


RESULTS
The overall response rate was 63.5%. There was no significant interaction between envelope and ink color. The use of green ink compared to black significantly increased the response rate from 61.4% to 65.7% (OR 1.20, 95% confidence interval 1.02, 1.41). There was no overall effect of envelope color on response rate (62.3% brown and 64.8% white, OR 0.90, 95% confidence interval 0.76, 1.06) but there was significant heterogeneity between the general practices. When this general practice-envelope interaction was accounted for, brown envelopes had a significantly lower response rate than white ones (OR 0.49).


CONCLUSIONS
This study, along with existing evidence, has shown that the use of certain ink colors in postal questionnaires is likely to increase response rates relative to black ink. The effect of envelope color was inconsistent both within this study and between previous studies.
Taylor
Kate S M
KS
Department of Medicine and Therapeutics, University of Aberdeen, Polwarth Building, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom. ksmp@iahs.abdn.ac.uk
Counsell
Carl E
CE
Harris
Clare E
CE
Gordon
Joanna C
JC
Fonseca
Sofia C C
SC
Lee
Amanda J
AJ
D000368:Aged; D003116:Color; D016001:Confidence Intervals; D004867:Equipment Design; D005194:Family Practice; D005260:Female; D006306:Health Surveys; D006801:Humans; D007281:Ink; D008297:Male; D016017:Odds Ratio; D010300:Parkinson Disease / Q000175:diagnosis*; D018579:Patient Selection; D011795:Surveys and Questionnaires