Sampling procedure, data collection tools, and procedure

Participants were selected from all female students of the university using multistage sampling technique. Probability proportionate sampling method was also applied to allocate the sample size according to the strata. The strata are categorized based on the batch/academic year of students. In order to select colleges and schools, simple random sampling techniques were applied.

Pretest was administered to 22 students, which accounts for 5%. Regarding their background, all of them were selected from similar socioeconomic status. These students were not involved in the main study.

Structured self-administered questionnaires were used. The questionnaire items were adapted from previous studies.13,30,31 Some terms were given operational definitions. For instance, class absence was defined as when students miss individual classes because of PD during the last month prior to the data collection and school absence was to mean when students miss a school day due to primary dysmenorrheal pain during the last month prior to the data collection. The tool includes sociodemographic characteristics, student’s psychosocial factor and family planning history, dysmenorrheal status, menstrual characteristics, activities affected by PD, behavioral factors, and PD effect on student’s academic performance. The questionnaires also included visual analogue scale questions and multidimensional scoring system to assess the severity of PD.30 The questionnaires were translated to local languages.

Training for data collectors and supervisors was given in understanding the objective of the survey, methods of data collection, and ways of approaching the respondents. The supervisor checked the activities of each data collector and all the filled questionnaires for its completion, clarity, and proper identification of the respondents. Then, the questionnaires were checked again for the completion by the principal investigator.