The effect on mail survey response rates of covering letters and questionnaire cover design : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Marketing at Massey University, Palmerston North
High response rates are important in survey research because they reduce the potential for nonresponse bias. The objective of this research was to determine whether survey response rates could be increased by modifying the content, tone or appearance of covering letters, or by manipulating the design of questionnaire covers. The theoretical basis of the research was social exchange theory, a general explanation of survey participation that asserts that an individual's actions are motivated by the return these actions are expected to bring from others, and that a particular action depends on the balance between rewards, costs and trust- The research also incorporated ideas from direct marketing and advertising research. The research confirms that an altruistic cover letter appeal appears to be more effective than an egoistic appeal for university-sponsored surveys of the general public. The same conclusion seems likely to apply to any non-commercial survey sponsor. However, there was no evidence that simplicity, a friendly tone, or the presence of graphics increases the effectiveness of survey covering letters. Similarly, a personalised covering letter had no effect on response rate, response speed, or data quality. This result is contrary to the findings of a number of previous studies. The suggestion that likeability, a predictor of advertising effectiveness, might predict the effectiveness of questionnaire cover design in a mail survey, was weakly supported. In five out of six studies of questionnaire covers involving graphic designs, the more 'likeable' covers produced an average increase in response rate of approximately 2%. Some evidence was also found that, in the absence of an accompanying questionnaire, a highly contrastive cover design is more effective than a barely contrastive design. However, the most effective strategy is to include a questionnaire with every wave of a mail survey. Overall, it appears the effect of covering letters and questionnaire cover design on response rate will be marginal in a well-conducted mail survey. Nevertheless, these elements may reinforce other survey factors, and, in some circumstances, 'tip the balance' between response and nonresponse.