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Sensory discrimination triangle test in Excel

2019-01-23

This tutorial will help you design and analyze a sensory discrimination triangle test in Excel using the XLSTAT statistical software.

Dataset for running a discrimination triangle test in sensory analysis

An Excel sheet with both the data and the results can be downloaded by clicking on the button below:
Download the data

A brewer wishes to commercialize a new beer and would like to know if consumers will be able to differentiate the new product from a beer of its own line of products. To test the hypothesis that both beers are similar, he wishes to use a triangle test.

Goal of the triangle test

The goal of this analysis is to first generate a design of experiments for the beer tasting, then to analyze the results in order to know if the two products are well discriminated.

In the triangle test, three samples are presented to each assessor in different orders. Within these samples, the two are similar. Assessors have to identify the sample that is different from the others.

Setting up a design for a triangle test

Once XLSTAT is activated, select the XLSTAT-Sensory data analysis / Design for sensory discrimination test feature.

Once you have clicked on the button, the dialog box appears. Select the triangle test. The number of judges is 20 in this study. Then select the name of the products. Two names per beer are necessary so that the judge does not know in advance the different product (the samples of beer 1 are called A and C / those of beer 2 are called B and D).


After you have clicked on the OK button, the computations start and the results are displayed on a new Excel sheet.

The output table allows (see below) you to run the test for 20 assessors. Each judge tastes 3 samples in the designated order. He will have to recognize the beer present only once. The fourth column allows you to enter the judge's answer. The fifth one gives the correct answer. The last column allows you to enter the test result. Just enter one code for a correct answer (+ in our case) and another code for an incorrect answer (- in our case). Of course, other codes can also be used. Note: If you enter the results in the fourth column, the last column will be filled automatically.

The generated design is as follows:

Once the design table is filled, you can analyze the obtained tasting results.

Running a triangle test with XLSTAT

Select the XLSTAT-Sensory data analysis / Sensory discrimination test feature.

The dialog box appears. Select the triangle test in the Test type field and the Thurstonian model in the Method field. We select the yellow column of the design table in the Discrimination test results field and enter + as a code for the correct answer.

We wish to estimate both d' and probability of discrimination so we choose the estimate option and use an exact binomial distribution. For more details on these concepts please click on the Help button.

After you have clicked on the OK button, the computations start and the results are displayed on a new Excel sheet.

Interpretation of the results of a triangle test

The first table summarizes the selected options.

Then the test results and interpretation are given. Here, the p-value is lower than 0.05, so we can reject the null hypothesis that d' is equal to zero. Therefore, we suggest that each beer does not follow the same normal distribution. We can thus reject the hypothesis that beers are similar. Furthermore, the power of our test being very high we can conclude that our test is robust enough.

The next table gives the parameter estimates including the d'. All parameters are significantly greater than 0. The d' is almost equal to 3 which is very high indicating a large difference between the two beers.

To sum up, the consumers managed to discriminate the new beer from the older one. The brewer can assume that this new product will be well identified by consumers.

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