Development and reliability testing of a food store observation form

J Nutr Educ Behav. 2013 Nov-Dec;45(6):540-8. 
Authors: Rimkus L, Powell LM, Zenk SN, Han E, Ohri-Vachaspati P, Pugach O, Barker DC, Resnick EA, Quinn CM, Myllyluoma J, Chaloupka FJ.

Objective: To develop a reliable food store observational data collection instrument to be used for measuring product availability, pricing, and promotion. Design: Observational data collection. Setting: A total of 120 food stores (26 supermarkets, 34 grocery stores, 54 gas/convenience stores, and 6 mass merchandise stores) in the Chicago metropolitan statistical area. Main Outcome Measures: Inter-rater reliability for product availability, pricing, and promotion measures on a food store observational data collection instrument. Analysis: Cohen's kappa coefficient and proportion of overall agreement for dichotomous variables and intra-class correlation coefficient for continuous variables. Results: Inter-rater reliability, as measured by average kappa coefficient, was 0.84 for food and beverage product availability measures, 0.80 for interior store characteristics, and 0.70 for exterior store characteristics. For continuous measures, average intra-class correlation coefficient was 0.82 for product pricing measures; 0.90 for counts of fresh, frozen, and canned fruit and vegetable options; and 0.85 for counts of advertisements on the store exterior and property. Conclusions and Implications: The vast majority of measures demonstrated substantial or almost perfect agreement. Although some items may require revision, results suggest that the instrument may be used to reliably measure the food store environment.

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