from the A-not-A test.
- Data type is binary.
The A-not-A discrimination test is a
variation of the paired comparison test. It is an unspecified test
with a probability of guessing of 0.5.
The panellist is presented with the
first product (A), which is then removed after evaluation.
A second product is then presented,
and the panellist decides whether it is the same as A or not. As
part of the test design multiple products may be compared with A in a monadic
protocol. The order of the samples is randomized.
- Treat Sessions/Replicates separately: If the
data has been gathered over different sessions, or there are different
replicates, these can be analysed separately.
Product: Select which product should be your reference product. This is the
first product in the test(A).
If yes, apply the continuity correction
for 2x2 contingency tables.
- Number of Decimals for Values: Required number
of decimals for values given in the results.
- Number of Decimals for P-Values: Required number
of decimals for any p-values given in the results.
Results and Interpretation
- Contingency table: This is a n x 2
contingency table of the responses, where n is the number of products.
The first row totals the responses when the reference product (A) was tested.
Subsequent rows total the responses when the other products were tested.
- A chi-squared test is then performed on the
contingency table. The following values are returned:
- Chi-squared value
- The Critical Chi-Squared value at a 5%
- Degrees of freedom
- P-value at 5% significance
the p-value is < 0.05 for the chi-squared test, it can be concluded that the
reference product (A) is significantly different to the other products. Note that
even if you conclude a difference, this does not imply similarity.
D-prime indicates the size of the
difference between the products. The following values are returned:
- Lower and upper 95% confidence intervals for
- P-value for Fisher’s Exact Test performed on
the contingency table.
Note that if one of the cells in the contingency table is zero, the d-prime cannot be calculated.
- The R package sensR (Rune Christensen and Per B.
Brockhoff) is used.
- The AnotA
function is used to calculate d-prime.
- ISO 8588:1987 – Sensory Analysis
– Methodology – ‘A’ – ‘not A’ Test
- Lawless, H.T. and Heymann,
H. (2010). Sensory Evaluation of Food – Principles and
Purpose To provide an analysis of data collected using the napping methodology. Data Format Napping.xlsx For EyeOpenR to read your data the first five columns must include the following in the specified order: Assessor, Product, Session, Replica and ...
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