This study was designed as a randomized controlled trial using a Solomon four-group experimental design to evaluate the effectiveness of a food safety training program. The study was conducted among food service employees working in municipal facilities. The Solomon four-group design was used to control for potential pretest sensitization effects while assessing the true impact of the intervention. Participants were randomly assigned to four groups using a randomization method. Each group included approximately equal numbers of participants. The intervention consisted of a face-to-face food safety training program developed based on identified needs. The training content included personal hygiene, food safety principles, and safe food preparation practices. The training sessions were delivered in structured modules. Data were collected using a structured questionnaire developed based on the literature and expert opinions. The questionnaire included sections assessing participants' knowledge, attitudes, and practices related to food safety. Pre-test and post-test assessments were conducted according to the Solomon four-group design. Data collection procedures and study implementation followed standardized protocols to ensure consistency. Participants were adults aged 18 years and older, able to communicate effectively, and voluntarily agreed to participate in the study. Ethical approval was obtained prior to the study, and all participants provided informed consent.

Methods Study Design and Setting This study was designed as a randomized controlled trial employing a Solomon four-group experimental design to evaluate the effectiveness of a food safety training program. The study was conducted among food industry employees working in municipal social facilities. The Solomon four-group design was selected to assess the true effect of the intervention while controlling for potential pretest sensitization bias, thereby strengthening both internal and external validity.

Participants and Sample Size A total of 278 food industry employees working in municipal facilities were assessed for eligibility. Sample size calculation was performed using the Epi Info software based on an assumed food safety training prevalence of 85.9%, derived from previous studies, with a 5% margin of error and a 95% confidence interval. The minimum required sample size was calculated as 186 participants. To account for potential data loss, this number was increased by 10%, resulting in a final target sample size of 200 participants.

Eligible participants were adults aged 18 years or older, employed in the food sector, and possessing at least basic literacy skills. Individuals who declined participation or had communication barriers were excluded from the study.

Reasons for exclusion and participant flow throughout the study are presented in Figure 1.

Randomization and Group Allocation Following eligibility assessment and informed consent, 200 participants were randomly allocated into four groups using a random numbers table, with 50 participants assigned to each group. The randomization process, group allocation, intervention exposure, follow-up, and final analysis numbers are summarized in Figure 1.

1. Intervention Group 1 (Pretest + Training + Posttest)
2. Intervention Group 2 (Training + Posttest)
3. Control Group 1 (Pretest + Posttest)
4. Control Group 2 (Posttest only) The flow of participants through the study and group allocation process is illustrated in Figure 1.

Intervention Development of Training Content Baseline data obtained from Intervention Group 1 and Control Group 1 (the pretested groups) were analyzed to identify gaps in food safety knowledge, attitudes, and practices. These baseline findings were used to inform and tailor the content of the food safety training program, ensuring that the intervention addressed participants' identified needs.

Based on this needs assessment, a structured training program consisting of three modules was developed:

1. Personal hygiene knowledge, attitudes, and practices
2. Workplace hygiene knowledge, attitudes, and practices
3. Safe food preparation processes Delivery of the Training Program The training intervention was delivered face-to-face by the research team in designated training halls within municipal facilities. The program consisted of three sessions, each comprising a 35-minute structured lecture followed by a 10-minute question-and-answer and discussion period. A 15-minute break was provided between sessions, and a maximum of 25 participants attended each session.

Participants in the intervention groups received the training program, whereas no intervention was applied to the control groups during the study period. To ensure ethical standards, control group participants were offered the same training after completion of posttest data collection.

Data Collection Instruments Data were collected using a structured questionnaire developed by the researchers based on relevant literature and expert consultation. The questionnaire comprised five sections with a total of 64 items assessing sociodemographic characteristics, previous food safety training, food safety knowledge, attitudes and practices. A pilot test was conducted with 10 food industry employees prior to data collection, and necessary revisions were made to improve clarity and relevance. The timing of pretest and posttest assessments, as well as the two-month follow-up period, are illustrated in Figure 1.

Details of the questionnaire items and scoring procedures are provided in the Supplementary Material.

Inclusion Criteria:

• Being 18 years of age or older
• Working in the food sector
• Having at least basic literacy skills

Exclusion Criteria:

• Refusing to participate in the study
• Having communication difficulties

Preventing shared data from influencing the responses of other participants