Design and participants
This quasi-experimental study was conducted online between August 10 and October 14, 2016. Participants were recruited through a study notification published on 1) a website managed by Medicus Shuppan Publishers Co., Ltd., a large Japanese publisher in nursing and medical sciences, 2) a job search site for midwives and nurses, and 3) Facebook. Macromill, Inc., an online survey company, posted the study invitation on the abovementioned media, and eligibility was confirmed by screening questions when the participant responded. The inclusion criteria were possession of a national nurse license and previous work experience in obstetrics or pediatrics, including neonatal intensive care units and growing care units. As of 2008, applicants for a midwife license in Japan must have a national nurse license.Participants were allocated to one of three groups: Group 1 received a “benefits of breastfeeding” text, Group 2 received a “risks of formula feeding” text, and Group 3 received a control text. Participants answered the questionnaire before and after reading the intervention text. The group allocation was not random; instead, participants were allocated by a computer system that balanced the number of participants in each group. Specifically, a new participant was assigned to the group with the smallest number of participants who had completed the pre-test questionnaire. After completing the pre-test questionnaire, the text of the allocated group was presented to the participants, after which they were invited to a post-test questionnaire. The whole process took approximately 30 minutes. Although participants were encouraged to read the text before proceeding to the post-test questionnaire, skipping the reading was possible and not monitored.