Reliability of a store observation tool in measuring availability of alcohol and selected foods

Alcohol and food items can compromise or contribute to health, depending on the quantity and frequency with which they are consumed. How much people consume may be influenced by product availability and promotion in local retail stores. We developed and tested an observational tool to objectively measure in-store availability and promotion of alcoholic beverages and selected food items that have an impact on health. Trained observers visited 51 alcohol outlets in Los Angeles and southeastern Louisiana. Using a standardized instrument, two independent observations were conducted documenting the type of outlet, the availability and shelf space for alcoholic beverages and selected food items, the purchase price of standard brands, the placement of beer and malt liquor, and the amount of in-store alcohol advertising. Reliability of the instrument was excellent for measures of item availability, shelf space, and placement of malt liquor. Reliability was lower for alcohol advertising, beer placement, and items that measured the "least price" of apples and oranges. The average kappa was 0.87 for categorical items and the average intraclass correlation coefficient was 0.83 for continuous items. Overall, systematic observation of the availability and promotion of alcoholic beverages and food items was feasible, acceptable, and reliable. Measurement tools such as the one we evaluated should be useful in studies of the impact of availability of food and beverages on consumption and on health outcomes.