BACKGROUND Internet has been broadly employed as a facilitator for epidemiological surveys, as a way to provide a more economical and practical alternative to traditional survey modes. A current trend in survey research is to combine Web-based surveys with other survey modes by offering the participant the possibility of choosing his/her preferred response method (i.e. mixed-mode approach). However, studies have also demonstrated that the use of different survey modes may produce different responses to the same questions, posing potential challenges on the use of mixed-mode approaches. METHODS In this paper, we have implemented a statistical comparison between mixed-mode survey responses collected via mail (i.e. paper) and Web methods obtained from a cross-sectional study in non-urban areas of Denmark. Responses provided by mail and Web participants were compared in terms of: 1) the impact of reminder letters in increasing response rates; 2) differences in socio-demographic characteristics between response groups; 3) changes on the likelihood of reporting health symptoms and negative attitudes towards environmental stressors. Comparisons were mainly performed by two sample t-test, Pearson's Chi-squared test and multinomial logistic regression models. RESULTS Among 3104 contacted households, 1066 residents decided to participate on the study. Out of those, 971 selected to respond via mail, whereas 275 preferred the Web method. The majority of socio-demographic characteristics between these two groups of respondents were shown to be statistically different. The use of mailed surveys increased the likelihood of reporting health symptoms and negative attitudes towards environmental stressors, even after controlling for demographic characteristics. Furthermore, the use of reminder letters had a higher positive impact in increasing responses of Web surveys when compared to mail surveys. CONCLUSIONS Our main findings suggest that the use of mail and Web surveys may produce different responses to the same questions posed to participants, but, at the same time, may reach different groups of respondents, given that the overall characteristics of both groups considerably differ. Therefore, the tradeoff between using mixed-mode survey as a way to increase response rate and obtaining undesirable measurement changes may be attentively considered in future survey studies.

中文翻译：

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环境健康研究中的自我报告数据：邮件与网络调查。


背景技术互联网已被广泛用作流行病学调查的促进者，作为一种提供比传统调查模式更经济实用的替代方式的方式。当前调查研究的趋势是将基于网络的调查与其他调查模式相结合，为参与者提供选择他/她喜欢的回答方法（即混合模式方法）的可能性。然而，研究也表明，使用不同的调查模式可能会对同一问题产生不同的回答，这对混合模式方法的使用提出了潜在的挑战。方法在本文中，我们对通过邮件（即纸质）收集的混合模式调查回复与从丹麦非城市地区的横断面研究获得的网络方法进行了统计比较。通过邮件和网络参与者提供的回复在以下方面进行了比较：1）提醒信对提高回复率的影响； 2) 响应群体之间社会人口特征的差异； 3）报告健康症状和对环境压力源的消极态度的可能性发生变化。比较主要通过两样本t检验、Pearson卡方检验和多项Logistic回归模型进行。结果 在 3104 户联系家庭中，1066 名居民决定参与研究。其中，971 人选择通过邮件回复，而 275 人则更喜欢网络方式。这两组受访者之间的大多数社会人口特征在统计上存在差异。即使在控制了人口特征之后，邮寄调查的使用也增加了报告健康症状和对环境压力源的消极态度的可能性。 此外，与邮件调查相比，使用提醒信对增加网络调查的回复具有更大的积极影响。结论 我们的主要发现表明，对于向参与者提出的相同问题，使用邮件和网络调查可能会产生不同的答复，但同时，考虑到两个群体的总体特征差异很大，可能会触及不同的受访者群体。因此，在未来的调查研究中，可以仔细考虑使用混合模式调查作为提高响应率的一种方式和获得不良测量变化之间的权衡。