2.2. Sampling
CHRONIC ILLNESS, PHYSICAL DISABILITY
Participants were fourth- to sixth-graders (10–12-year-olds) selected through stratified random sampling. The sample size was calculated considering the change in the mean and standard deviation of nutritional literacy scores based on the previous studies (Significance level = 0.05, Study power = 80%, Number of time repeats = 2.Effect size: 0.179 based on the study by Appleton et al. (Based on the above calculations, the sample size in each group was calculated at 131 individuals. A total of 300 participants (150 students for intervention and 150 controls) were selected to account for possible sample loss. The inclusion criteria were students' desire to participate in research, family's desire to cooperate in the study, study in the fourth, fifth and sixth grades of elementary school, having no chronic illness, having no physical disability, Iranian citizenship, and not participating in the sub-study 2.