Sensory Analysis: Simple Discrimination TestsThis Add-In creates an easy interface to some of the most common sensory tests: Triangle Test, Duo-Trio Test, Paired Comparison, and 2-Out-Of-5 tests.
Each of these is a chi-squared tests of proportions, with a given pair of probabilities for a "right" answer under the null hypothesis that the samples are not different. An example test for the Triangle Test and the original script are included with the Add-In.
The data table should contain a binary column to be tested. This column must have the Modeling Type Nominal. For best results with the Triangle Test and 2-Out-Of-5 Tests, assign a value label with Yes/No or Correct/Incorrect to ensure that the porportions are assigned properly.
The JMP documentation shows an example of the Test of Proportions.
Consumer and Market ResearchRe: Sensory Analysis: Simple Discrimination TestsHi, Paul.
The Chi-Squared is always a one-sided test. StatsExchange over on StackOverflow has a nice discussion on this.
So, following the guidelines on SensorySociety.org, the stated p-values are correct.
One could argue that we should perform a two-sided test instead. JMP offers that as an exact binomial test.
That test is not as well-known, and I haven't seen it recommended in the sensory analysis literature. I feel like I'm in a bit of a bind when it comes to reporting p-values for the user. The software is written to spec, but maybe it's not what a statistician would recommend generally.
What's your opinion?
Re: Sensory Analysis: Simple Discrimination TestsHello Melinda, thank you for your reply and for pointing me to the data.
I have a question --what was the alternative hypothesis used? I'm thinking that it should be that the proportion of Correct Answers > 0.3333, because that is evidence that there is truly a difference between products A and B. The triangle test is a discriminatory test, so we care about whether panelist choose the correct answer more than would be expected by chance.
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When I ran the test with the one-sided alternative hypothesis, I got a slightly different probability than was in the Distribution script supplied with the sample data. Not sure if this 2-sided Chi-Square test was intended to represent a triangle test.
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Regards, Paul
Re: Sensory Analysis: Simple Discrimination TestsAnd apparently there is a way to get to the sample data I packaged with the AddIn.
In JMP,
1) Go to View->AddIns.
2) Click the name of the Addin in the window that appears
3) Click the hyperlink for the addin Home folder.
Re: Sensory Analysis: Simple Discrimination TestsHi, Paul! My apologies. I didn't realize that you can't access a file packaged with an AddIn.
I've attached the file to the original post instead. Please make sure you have the current version. I uploaded a fresh copy yesterday. Please also let me know if you have questions or problems!
Re: Sensory Analysis: Simple Discrimination TestsAdding sensory tests is a nice feature. I use triangle tests a lot. How do I access the example for the Triangle Test? I have the add-in installed, and can open it. However, I don't see where the sample data is installed -- I looked in the Sample Data Library,is that where it's located? Thanks, Paul
