Design and Validation of a Questionnaire to Assess Determinants of the Functional Dairy Product Consumption and Preferences in Adults In Iran

The production of functional foods to prevent and manage diet-related chronic diseases is rising worldwide, including in Iran. It is essential to understand factors affecting the acceptance of functional foods. The present study was conducted to design a valid reliable questionnaire for assessing determinants of functional dairy product consumption and preferences in adults in Tehran, the capital city of Iran.

This study was a mixed-method (qualitative and quantitative) study. The questionnaire items were derived from the qualitative study results mixed with items obtained from the literature. Then, psychometric characteristics of the instrument, including content validity, face validity, internal consistency, and stability, were assessed. Cronbach's alpha, intra-class correlation coefficient, and kappa were assessed using SPSS Software v.21.

The primary question pool included 52 questions, which decreased to 33 after assessing the content validity index and ratio. The instrument's overall scale content validity index was 0.96. The internal consistency reliability of the attitude scale was calculated as 0.87. The kappa coefficient values for familiarity/unfamiliarity with functional dairy products and their consumption/non-consumption ranged 0.61–1. Intraclass correlation coefficient values ranged 0.69–1 for the frequency of functional dairy consumption, 0.73–0.86 for the degree of importance of product characteristics in affecting consumer choices, and 0.83–0.92 for the consumer views for the information on functional dairy products. The intraclass correlation coefficient for the attitude towards these products was 0.92, indicating the high test-retest reliability of the instrument.

The questionnaire designed in this study was a valid reliable instrument that could assess various factors affecting the consumption of functional dairy products and consumer preferences concerning these products.