The soup data frame has 1847 rows and 13 variables. 185
respondents participated in an A-not A discrimination test with
sureness. Before experimentation the respondents were familiarized
with the reference product and during experimentation, the respondents
were asked to rate samples on an ordered scale with six categories
given by combinations of (reference, not reference) and (sure, not
sure, guess) from 'referene, sure' = 1 to 'not reference, sure' = 6.
soupRESPfactor with 185 levels: the respondents in the study.
PRODfactor with 2 levels: index reference and test products.
PRODIDfactor with 6 levels: index reference and the five test product variants.
SURENESSordered factor with 6 levels: the respondents ratings of soup samples.
DAYfactor with two levels: experimentation was split over two days.
SOUPTYPEfactor with three levels: the type of soup regularly consumed by the respondent.
SOUPFREQfactor with 3 levels: the frequency with which the respondent consumes soup.
COLDfactor with two levels: does the respondent have a cold?
EASYfactor with ten levels: How easy did the respondent find the discrimation test? 1 = difficult, 10 = easy.
GENDERfactor with two levels: gender of the respondent.
AGEGROUPfactor with four levels: the age of the respondent.
LOCATIONfactor with three levels: three different locations where experimentation took place.
Christensen, R. H. B., Cleaver, G. and Brockhoff, P. B.(2011) Statistical and Thurstonian models for the A-not A protocol with and without sureness. Food Quality and Preference, 22, pp. 542-549.