Effect on survey response rate of hand written versus printed signature on a covering letter: randomised controlled trial [ISRCTN67566265]

Randomised controlled trial. Questionnaires about surgical techniques of caesarean section were mailed to 3,799 Members and Fellows of the Royal College of Obstetricians and Gynaecologists resident in the UK. Individuals were randomly allocated to receive a covering letter with either a computer printed signature or a hand written signature. Two reminders were sent to non-respondents. The outcome measures were the proportion of questionnaires returned and their time to return.The response rate was 79.1% (1506/1905) in the hand-signed group and 78.4% (1484/1894) in the scanned and printed signature group. There was no detectable difference between the groups in response rate or time taken to respond.No advantage was detected to hand signing the covering letter accompanying a postal questionnaire to health professionals.Large surveys of clinical practice are often conducted by postal questionnaire, as this is a practical and economical method of obtaining information. However, if the response rate is low, the respondents may represent a biased sample of the population. It is therefore desirable that the response rate to a postal survey be as high as possible, to ensure that there is sufficient statistical power and the findings are representative. One factor that may influence response rate is whether the covering letter that is sent out with the questionnaire is hand signed or bears a photocopied or printed signature. The rationale is that individuals who receive a hand signed covering letter may feel that the letter is more personalised to them, and hence may be more likely to complete and return the questionnaire than those who receive a letter with a printed signature.A recent systematic review [1] included a meta-analysis of randomised controlled trials investigating the effects of personalisation of covering letters accompanying postal questionnaires. The results suggested that an approach in the form of personalised letters, questionnaires or envelopes improved