Impact of Different Cover Letter Information and Incentives on Veterans’ Emotional Responses to an Unsolicited Mailed Survey About Military Traumas - Randomized, 3x2x2 Factorial Trial

Sep 13, 2026

Altering cover letter content in trauma-related research may reduce non-response bias, while also risking that participants feel unprepared for distressing survey questions. This study evaluated how changes in key cover letter information and promised incentives affected Veterans’ emotional responses after completing an unsolicited, mailed survey about military traumas. It tested direct and indirect pathways through participants’ careful reading, perceived informativeness, and preparation for the survey’s trauma content, using a randomized factorial design.

LanguageEnglish

CategoryPresentations

FormatPDF

Pages11

Reading Time4 min

AccessFree to download

Abstract

Background

Methods

Results

Conclusion

Keywords

Murdoch et al. BMC Medical Research Methodology (2022) 22:308 [https://doi.org/10.1186/s12874-022-01783-7](https://doi.org/10.1186/s12874-022-01783-7) RESEARCH Open Access Impact of different cover letter information and incentives on Veterans’ emotional responses to an unsolicited mailed survey about military traumas: a randomized, 3x2x2 factorial trial Maureen Murdoch1,2,3*, Barbara A Clothier2, Shannon Kehle‑Forbes2,3,4, Derek Vang5 and Siamak Noorbaloochi2,3 Abstract Background: Altering cover letter information to reduce non‑response bias in trauma research could inadvertently leave survey participants unprepared for potentially upsetting questions. In an unsolicited, mailed survey, we assessed participants’ change in affect post‑survey after altering key cover letter information and promising different incen‑ tives. We tested direct and indirect effects of participants carefully reading the cover letter on changes in their affect post‑survey. Methods: In a 3X2X2 randomized, factorial trial, 480 male and 480 female, nationally representative Veterans who were applying for posttraumatic stress disorder disability benefits were randomized to receive one of 12 different cover letters. The cover letters provided general versus more explicit information about the survey’s trauma content and how their names were selected for study; we also promised different incentives for returning the survey. The main outcome was change in affect post‑survey. We examined five potential moderators: combat or military sexual trauma exposure, posttraumatic stress disorder or serious mental illness diagnosis, and recency of military service. Mediators between reading the cover letter carefully and post‑survey affect included how participants rated the cover letters’information and whether they thought the cover letters prepared them for the survey’s content. A Bonferroni cor‑ rected alpha of 0.003 was the threshold for statistical significance. Results: One hundred ninety men and 193 women reported their pre‑and post‑survey affect. Across all study conditions, out of 16 possible points, the net change in affect post‑survey was less than a quarter‑point for men and women. Mean changes in post‑survey affect did not differ statistically significantly across any of the study factors (ps> 0 . 06); nor were there statistically significant interactions between any of the study factors and the 5 moderators after accounting for multiple comparisons (ps > 0. 02) . After controlling for pre‑survey affect, reading the cover letter carefully had small effects on changes in post‑survey affect, with larger associations seen in the women compared to men. Mediators’ effects were often in opposite directions for men and women. *Correspondence: [Maureen.Murdoch@va.gov](Maureen.Murdoch@va.gov) 1 Section of General Internal Medicine, Minneapolis VA Health Care System, One Veterans Drive (111‑0), Minneapolis, MN 55417, USA Full list of author information is available at the end of the article This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2022. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material isnot included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit [http://creativeco](http://creativeco)[mm

FAQs

What was the study’s main goal?

To determine whether different cover letter information and incentives change Veterans’ emotional responses after an unsolicited mailed trauma survey.

How was the study designed?

A randomized, 3x2x2 factorial trial assigned nationally representative Veterans to one of 12 different cover letters.

What influenced participants’ post-survey affect according to the results?

Reading the cover letter carefully showed small effects on changes in post-survey affect, with small differences observed by gender and mediator effects often differing by gender.

Sep 13, 2026

Uploaded by Quinn Holloway