Nutritional literacy self-assessment questionnaire for students (NL-SF12)

The nutritional literacy self-assessment questionnaire for students (NL-SF12) is a tool developed by Zhang et al. [13]. in 2022 to evaluate students’ cognitive performance and skills related to nutrition. The original form of the questionnaire, NL-43, consists of 43 items. However, the short form of this questionnaire contains 12 questions and six dimensions [30]. These six dimensions include knowledge, understanding, obtaining skills, applying skills, skill application, interactive skills, and critical skills. Knowledge refers to basic nutritional knowledge. Understanding is the ability to read and comprehend nutritional information and recommendations. Obtaining skills is the ability to search for and get nutritional information or services. Skill application refers to applying nutritional knowledge or assistance to maintain a healthy diet. Interactive skills are the ability to interact with food environments that surround us socially and avoid poor eating behaviors or unhealthy food environments. Critical skills are the ability to critically reflect on nutritional information or recommendations based on individual needs. Participants respond to questions using a Likert scale ranging from strongly disagree (1) to agree (5) strongly. In Gao et al.‘s study [30], Cronbach’s alpha for the NL-SF12 tool was reported as 0.89.

After obtaining permission from the tool designer [30], the English version of this questionnaire was translated back and forth, first by two specialized translators independently translating it into Persian without knowledge of each other’s work. Then, both translations were put together, and the best words were selected to create a single version. In the next stage, this Persian text was translated back into English by two translators proficient in English without knowing each other’s work or the original questionnaire text. The translated text was then checked for conformity with the original questionnaire before data collection. To determine content validity ratio (CVR) and relevance ratio, the questionnaire was given to 10 faculty members at Ardabil University of Medical Sciences. The content validity index (CVI) was evaluated separately by experts using three criteria: simplicity, relevance, and clarity on a four-part spectrum (e.g., from very simple to somewhat complex and complex) for each question. Finally, the content validity index and content validity ratio were obtained as 0.91 and 0.88. Additionally, Cronbach’s alpha for the nutritional literacy subscales ranged from 0.73 to 0.89, with an overall nutritional literacy score of 0.84.

This study conducted both Exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) to confirm the factorial structure and the construct validity of the NL-SF12. An exploratory factor analysis with varimax rotation was used to assess the construct validity of the NL-SF12. The results showed that the Kaiser-Meyer-Olkin (KMO) was 0.840, and Bartlett’s test of sphericity was statistically significant (p < 0.001, χ² = 1912.335, df = 102), indicating the relevance and appropriateness of the data for conducting the factor analysis. Six factors were extracted that consisted of 12 items and explained 59.57% of the total variance. Also, all items were retained due to the commonalities of < 0.2 and factor loading of < 0.3.

The CFA model was tested using maximum likelihood estimates. The goodness of fit of the model was appraised using multiple criteria including the following: χ²/df < 3, Root Mean Square Error of Approximation (RMSEA) < 0.08, Incremental Fit Index (IFI) > 0.90, Normed Fit Index (NFI) > 0.90, Comparative Fit Index (CFI) > 0.90, Goodness of Fit Index (GFI) > 0.90, and Tucker Lewis Index (TLI) > 0.90 [31]. Evaluating the fit of structural equation models: Tests of significance and descriptive goodness-of-fit measures. Methods of psychological research online, 8(2), 23–74.). The goodness-of-fit indices in CFA indicated acceptable values: χ²/df = 2.621, RMSEA = 0.059, IFI = 0.967, NFI = 0.948, CFI = 0.957, GFI = 0.926, and TLI = 0.942.

To assess the reliability of the scale, Cronbach’s alpha coefficient (> 0.7) and intraclass correlation coefficient (ICC) (> 0.75) were calculated for the entire scale [32, 33]. The results showed that the NL-SF12 has acceptable reliability. The overall Cronbach’s alpha was 0.86 (knowledge = 0.79, understanding = 0.82, obtaining skills = 0.88, applying skills = 0.83, interactive skills = 0.81, and critical skills = 0.89). The ICC was 0.83 over two weeks.