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• Functional data analysis (FDA) for Rating Scale (RS) Time-Intensity (T-I) data. • The mean RS functional curves and their 1st and 2nd derivative curves. • The index of efficiency (A.RS) based on area under curve for percentage (%) relief. • Functional analysis of variance (FANOVA) for detection of group effects. A longitudinal study was undertaken recently in the USA to investigate the perceptual efficacy of a supplement tablet. Efficacy was assessed using an 11-attribute 5-point Rating Scale (RS). The RS diary time-intensity data were analyzed using functional data analysis (FDA). The mean RS functional curves and their 1st and 2nd derivative curves are produced. Attribute intensities (symptom relief) are compared to baseline measures. Two indices of efficacy were used to measure reduction in symptom severity. Results show symptoms decreased over the 12-week study with use of the tablet. The focus of this paper is on applied use of FDA and the new index A.RS which shows advantages by providing examination of the full range of longitudinal data (0–84 days) and a percentage efficacy index versus a traditional efficacy index that is based on the difference between just two time points (day 0 and day 84). The analytic methods in this paper have relevancy for sensory and consumer time-intensity research and longitudinal study. [ABSTRACT FROM AUTHOR]