Thicker paper and larger font increased response and completeness in a postal survey.

Objective: To investigate the effect of font size and paper thickness on the response to, and completion of, a self-completion postal questionnaire among older people with joint pain.
Study Design and Setting: Randomized trial. People aged 50 years and older with joint pain who consulted a general practitioner at one of five general practices in Central Cheshire were sent a postal questionnaire. Questionnaire format (large or small font size, thick or thin paper) was randomly allocated using a 2 x 2 factorial design.
Results: Questionnaires were received from 502 out of 650 participants (crude response 77%). Response was significantly higher for participants receiving questionnaires with a larger font size (79.3% vs. 75.2%; hazard ratio 1.26, 95% confidence interval: 1.02, 1.56). Paper thickness had no significant effect on response. Completion (measure by assessing double-page turnover error) was increased in participants receiving questionnaires printed on thicker paper (3.2% vs. 7.1%; P=0.049) but was not affected by font size.
Conclusion: This study demonstrates that questionnaires in larger font and on thicker paper may produce higher and more complete responses than surveys using standard size font and standard thickness paper, and should therefore be considered in studies among older people.