Questionnaire design: carry-over effects of overall acceptance question placement and pre-evaluation instructions on overall acceptance scores in central location tests.

Question placement and usage of pre-evaluation instructions (PEI) in questionnaires for food sensory analysis may bias consumers' scores via carry-over effects. Data from consumer sensory panels previously conducted at a central location, spanning 11 years and covering a broad range of food product categories, were compiled. Overall acceptance (OA) question placement was studied with categories designated as first (the first evaluation question following demographic questions), after nongustation questions (immediately following questions that do not require panelists to taste the product), and later (following all other hedonic and just-about-right [JAR] questions, but occasionally before ranking, open-ended comments, and/or intent to purchase questions). Each panel was categorized as having or not having PEI in the questionnaire; PEI are instructions that appear immediately before the first evaluation question and show panelists all attributes they will evaluate before receiving test samples. Postpanel surveys were administered regarding the self-reported effect of PEI on panelists' evaluation experience. OA scores were analyzed and compared (1) between OA question placement categories and (2) between panels with and without PEI. For most product categories, OA scores tended to be lower when asked later in the questionnaire, suggesting evidence of a carry-over effect. Usage of PEI increased OA scores by 0.10 of a 9-point hedonic scale point, which is not practically significant. Postpanel survey data showed that presence of PEI typically improved the panelists' experience. Using PEI does not appear to introduce a meaningful carry-over effect.