The present study validates a revised scale measuring individuals’ level of the ‘engagement in dietary behaviour’ aspect of ‘critical nutrition literacy’ and describes how background factors affect this aspect of Norwegian tenth-grade students’ nutrition literacy.

Data were gathered electronically during a field trial of a standardised sample test in science. Test items and questionnaire constructs were distributed evenly across four electronic field-test booklets. Data management and analysis were performed using the RUMM2030 item analysis package and the IBM SPSS Statistics 20 statistical software package.

Students responded on computers at school.

Seven hundred and forty tenth-grade students at twenty-seven randomly sampled public schools were enrolled in the field-test study. The engagement in dietary behaviour scale and the self-efficacy in science scale were distributed to 178 of these students.

The dietary behaviour scale and the self-efficacy in science scale came out as valid, reliable and well-targeted instruments usable for the construction of measurements.

Girls and students with high self-efficacy reported higher engagement in dietary behaviour than other students. Socio-economic status and scientific literacy – measured as ability in science by applying an achievement test – did not correlate significantly different from zero with students’ engagement in dietary behaviour.

Critical nutrition literacy (CNL), as an increasingly important area in public health nutrition, can be defined as the ability to critically analyse nutrition information, increase awareness and participate in action to address barriers to healthy eating behaviours. Far too little attention has been paid to establishing valid instruments for measuring CNL. The aim of the present study was to assess the appropriateness of utilizing the latent scales of a newly developed instrument assessing nursing students’ ‘engagement in dietary habits’ (the ‘engagement’ scale) and their level of ‘taking a critical stance towards nutrition claims and their sources’ (the ‘claims’ scale).

Data were gathered by distributing a nineteen-item paper-and-pencil self-report questionnaire to university colleges offering nursing education. The study had a cross-sectional design using Rasch analysis. Data management and analysis were performed using the software packages RUMM2030 and SPSS version 20.

School personnel handed out the questionnaires.

Four hundred and seventy-three students at ten university colleges across Norway responded (52 % response rate).

Disordered thresholds were rescored, an under-discriminating item was discarded and one item showing uniform differential item functioning was split. The assumption of item locations being differentiated by stages was strengthened. The analyses demonstrated possible dimension violations of local independence in the ‘claims’ scale data and the ‘engagement’ scale could have been better targeted.

The study demonstrates the usefulness of Rasch analysis in assessing the psychometric properties of scales developed to measure CNL. Qualitative research designs could further improve our understanding of CNL scales.