This is a randomized controlled trial comparing the effects of peer education and traditional education on increasing knowledge and awareness of secondhand and thirdhand tobacco smoke exposure among geriatric care program students. Tobacco use and passive smoking are serious public health problems that cause millions of deaths each year and are highly prevalent among university students. Not only smoke dispersed in the air (secondhand smoke), but also toxic residues that accumulate on surfaces and can be absorbed through the skin and ingestion (thirdhand smoke) carry carcinogenic risks. It is a professional obligation for these students, who are the health professionals of the future, to protect the vulnerable elderly population they will serve from this exposure (especially residues carried on clothing/hair). It is also aimed to protect their own health against the risk of smoking triggered by occupational stress. Traditional education that only imparts information may be insufficient in changing behavior. Peer education based on Social Learning Theory offers a sincere and effective alternative that encounters less resistance among young people. While existing experimental studies in the literature generally focus on "active smoking and motivation to quit," this study fills an important gap by focusing on passive and third-hand exposure. If successful, this peer education model could be implemented as a standardized educational module at the national level in university campuses.

Research hypotheses:

H1: Students who receive peer education have higher levels of knowledge about secondhand smoke than students who receive traditional education.

H2: Students who receive peer education have higher levels of awareness about thirdhand smoke than students who receive traditional education.

H3: There is a difference between the pre- and post-intervention and between the experimental and control groups in terms of students' average scores for their awareness level of secondhand smoke.

H4: There is a difference between the pre- and post-intervention and between the experimental and control groups in terms of students' average scores for their knowledge level of thirdhand smoke.

The research will be conducted at the Karabük University Health Services Vocational School Elderly Care Program between March 1, 2026, and March 1, 2027.

The research population consists of first- and second-year students enrolled in the Karabük University Health Services Vocational School Elderly Care Program. Although there are a total of 144 students registered in the department records, the number of students actively attending classes has been determined to be 124. Of these students, 68 are first-year students and 56 are second-year students. No sample selection was made in the research; the aim was to reach the entire population actively receiving education.

Prior to the intervention, students who would serve as "Peer Educators" were selected based on volunteerism and academic achievement criteria. A total of 8 students, 4 from the 1st grade and 4 from the 2nd grade, were included in the "Educator" group and were not included in the sample group of the study.

After the peer educators were separated, the number of active students remaining in the universe where the study was conducted was 116.

The sample size for the study was calculated using the G*Power (v3.1.9.7) statistical software package. In the study, since the tobacco exposure awareness levels of the experimental and control groups were to be compared at three different time points (pre-test, post-test, and 21st day T3 follow-up measurement), the power analysis was performed based on the Repeated Measures ANOVA (Within-Between Interaction) design. The "medium effect size" (f = 0.25), which is the standard accepted in studies measuring the effect of educational interventions, was used as a reference. When the Type I error rate (α = 0.05), test power (1-β = 0.80), number of groups (2), and number of repeated measures (3) were included in the model, the minimum total sample size required to statistically detect an interaction between groups was calculated to be 28. Considering the 10% potential data loss (absenteeism, discontinuation of the test, etc.) that may occur due to the time-series structure of the study, the minimum safe sample size to be achieved was updated to 32. It was observed that the current active population size (N=116) more than meets this minimum value; therefore, it was decided not to proceed with sample selection and to include the entire active population in the study.

Randomization and Group Formation: After peer educators (n=8) were separated, the remaining 116 active students (1st grade: 64, 2nd grade: 52) were stratified according to their grade levels and then assigned to two groups using a "Computer-Assisted Simple Random Number Table." Thus, the experimental and control groups were numerically equalized (n=58), and the effect of grade level differences was controlled (through stratification).

• Experimental Group (Peer Education): 58 Students (32 from 1st Grade, 26 from 2nd Grade)
• Control Group (Traditional Education): 58 Students (32 from 1st Grade, 26 from 2nd Grade)

Prevention of Interaction: The most significant factor threatening the internal validity of the study is the sharing of educational content among students in the same school environment. To minimize this risk, participants will be informed about "Research Confidentiality and Individual Impact" regarding not sharing the information learned during the training with their peers in the other group until the final test is completed.

The question "Did you discuss the educational content with anyone from the other group during this process?" will be added to the final test data collection form, and the data of participants found to have interacted will be flagged for exclusion from the analysis.

To prevent the artificial increase in performance resulting from observation awareness (Hawthorne Effect), the control group will also receive training at the same time to equalize the 'level of interest' between groups, and the main hypothesis of the study will not be disclosed to participants to control for expectation bias.

Pilot Study: A pilot study will be conducted prior to the main study to test the comprehensibility of data collection tools and evaluate the feasibility of educational materials (duration, flow, technical issues).

In order to maintain the sample size of the main study, the pilot study will be conducted with 12 students enrolled in the Audiometry Program at Karabük University School of Health Services Vocational School, who are not included in the population but have similar sociodemographic characteristics. During the pilot application process: it will be examined whether the survey questions and scale items are found to be clear and understandable by the students, the average completion time of the surveys will be determined, and any potential technical or pedagogical issues that may arise during the presentation of peer education and classical education materials will be observed. The data obtained from the pilot study will not be included in the analysis of the main study.

Pre-Test (T0)

A pre-test (T0) consisting of an 'Individual Information Form, Passive Exposure Information Test, and Third-Hand Smoke Awareness Scale' will be administered to both groups at the beginning of the study. Pre-test data will be collected immediately before the educational intervention begins.

Final Test Immediately after completing the training program in both groups (T1) and on Day 21 (T2), participants were administered a final test consisting of a 'Knowledge Test on Passive Exposure and Awareness Scale on Third-Hand Smoke' to compare the effectiveness of the methods.

The data obtained from the study will be analyzed using statistical software ( IBM SPSS Statistics). The normality of the data distribution will be assessed using the Shapiro-Wilk and Kolmogorov-Smirnov tests, and the homogeneity of variances will be evaluated using the Levene test. Descriptive statistics will be presented as counts, percentages, means, and standard deviations.

To test the homogeneity of the groups' initial characteristics (pre-test scores and demographic data), the Chi-square test (Fisher's Exact Test when expected cell frequencies are less than 5) will be used for categorical data, and the Independent Samples t-test will be used for continuous variables.

A Two-Way Repeated Measures ANOVA will be used to compare the change in the effectiveness of the educational methods (Peer Education and Traditional Education) over time (Pre-test [T0], Post-test [T1], and Follow-up [T3]) and the interaction between the groups (Experimental and Control). Prior to this analysis, the sphericity assumption will be checked using the Mauchly Test, and the Greenhouse-Geisser correction will be applied if the assumption is not met. If the interaction is found to be significant, Bonferroni-corrected post-hoc tests will be performed to determine the time point from which the difference originates.

If the data do not meet the assumption of normal distribution, the Friedman Test will be used for within-group repeated measures; the Bonferroni-corrected Wilcoxon Signed-Rank Test will be used for pairwise comparisons when the difference is significant; and the Mann-Whitney U test will be used for between-group comparisons. The statistical significance level will be set at p < 0.05.

Safety Measures to Be Taken During Implementation:

This research is non-interventional and education-based. There is no risk of physical, mental, or social harm to participants. Ethical principles will be adhered to throughout the research process in accordance with the Declaration of Helsinki.

Informed consent will be obtained from participants prior to the research, and it will be clearly stated that participation is entirely voluntary. Participants will have the right to withdraw from the research at any time without giving any reason. The data obtained will be used solely for scientific purposes, personal identity information will be kept confidential, and will not be shared with third parties. Data will be stored in an encrypted environment and will only be accessible to researchers. As the research is an education-based awareness initiative, no negative effects on participants are anticipated.

Inclusion Criteria:

• Be enrolled in the first or second year of the Elderly Care Program at Karabük University School of Health Services,
• Agree to participate in the study voluntarily,
• Be able to participate in the training process and follow-up measurements (T0, T1, and T2),
• Be able to respond to Google Forms applications via a device with internet access (phone, tablet, computer)

Exclusion Criteria:

• Receiving any training on tobacco use, secondhand and thirdhand smoke exposure within 6 months,
• Participants who incomplete survey forms or leave at least one scale blank,
• Students who do not participate in training programs and for whom follow-up measurements cannot be taken,
• Those who cannot complete all stages of the study due to health reasons or absenteeism.

To prevent "selection bias" in assigning participants to groups in the study, the "Sequential Numbering, Closed Envelope Method" will be used.

Random Assignment List: Participants will first be divided into two separate groups: "1st Grade" and "2nd Grade." Using a Computer-Assisted Simple Random Number Table, two different "Group Assignment Lists" (Experimental and Control) will be created separately for each group.

Preparation of Envelopes: Opaque envelopes of different colors will be prepared for each class level. Group assignment cards will be placed inside the envelopes according to the randomly generated lists.

Implementation: Participants will be invited to an informational meeting before the training begins. At the briefing meeting, participants will be asked about their grade levels in order of arrival. Then, they will be asked to draw the next numbered sealed envelope from the box corresponding to their grade level, completing the group assignment process.