Study design
This is a cross-sectional-analytical study. The study population included all male high school students in Hamadan in the academic year 2020; 414 of whom were selected by stratified random sampling, in such a way that the research community was divided into eight classes based on the two education districts of Hamadan, public and private schools and the first (seventh, eighth and ninth grade) and second (tenth, eleventh and twelfth) grades of secondary schools. Then, the number of samples for each class was selected according to the number of students in each class of the research community.
Entry and exit criteria
Students studying in high school, and living in Hamadan were among the entry criteria, and the agreement form was not filled by students and their parents was the criterion for leaving the study.
Instrument
The data collection tool was an researcher-made self-rating questionnaire that was designed after conducting semi-structured interviews with students and the recommended process of Ajzan (12) and Francis (4) was used in its construction. According to these researchers, except behavior, the variables of the theory of planned behavior include psychological (internal) constructs. Thus, each predictor variable can be measured directly or indirectly by asking respondents about their general attitudes; for example, by asking respondents about specific behavioral beliefs and evaluations. However, since neither of these two methods is complete, a combination of these two methods should be used to construct a questionnaire for measuring the variables of the theory of planned behavior. On the other hand, these researchers use the principle of Target, Action, Context and Time (TACT) to define target behavior and divide behavior into these four elements. Also, in the arrangement of items, those related to measuring attitude are presented along with those measuring subjective norms and perceived behavioral control. Other cases of constructing a questionnaire for measuring the variables of the theory of planned behavior are presented in detail in the mentioned studies.
After obtaining the consent form of the participants as well as their parents, the students participated in the study voluntarily. The response rate of the participants in the present study was 87%. In this study, a questionnaire including questions was used which was related to students' knowledge and behavior.
Part one
The first part of the questionnaire was related to the demographic variables of the participants (7 items).
Part two
The second part to the knowledge items (5 items), behavioral perception (6 items), subjective norms (6 items), perceived controlled behavior (6 items), behavioral intention (3 items) and behavior (3 items). Items about knowledge were 4-choice questions (one true choice/three wrong choices) with a minimum score of zero and a maximum score of 5 (example: Which occupant should wear a seat belt?), items about attitudes were questions with five-points Likert Scale, with a minimum score of 6 and a maximum score of 30 (example: I like to wear a helmet while cycling), subjective norms were questions with five-points Likert Scale with a minimum score of 6 and a maximum score of 30 (Example: People who matter to me recommend that I fasten my seat belt in the car), items about perceived behavioral control were questions with five-points Likert Scale with a minimum score of 6 and a maximum score of 30 (example: In any situation, I can cross from pedestrian crossings, overpasses and authorized underpasses), behavioral intention questions with five-points Likert Scale had a minimum score of 3 and a maximum score of 15 (example: I plan to use a helmet for cycling for greater safety from now on) and behavioral items were questions with five-points Likert Scale with a minimum score of 3 and a maximum score of 15 (example: I fasten my seat belt in the car).
In order to analyze the face validity of the questionnaire, it was given to 10 students participating in the study and 10 health education and health promotion specialists in the field of health and safe traffic behaviors, and the level of difficulty and comprehensibility of the items were investigated and corrections were made. To measure the content validity by quantitative method, two coefficients of content validity ratio (CVR) and content validity index (CVI) were used with using a panel of experts. Content validity ratio was confirmed considering the numerous experts used and the score higher than 0.62 in the Lawshe table, and a score higher than 0.79 was used to confirm the content validity index. Also, in this study, confirmatory factor analysis method was used to measure and determine the structural validity.
Data analysis
To evaluate the reliability, the questionnaire was distributed among 30 students and a Cronbach's alpha of 0.95 was obtained. The collected data were analyzed using SPSS version 21 and appropriate statistical test with a significance level of 0.05.