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*From*: Bill Norwood <bnorwood111@gmail.com>*Date*: Fri, 10 Nov 2017 15:58:25 -0500

Hi Jeremy, - I am afraid that that one is too far outside the areas that I have studied, but I will see if anyone on the Phys-L network might have any remark(s). Best, Uncle Bill On Fri, Nov 10, 2017 at 7:42 AM, jeremy fair wrote: > Hi Uncle Bill, > When it comes to scientific “stuff” you are the family expert so perhaps > you can point me in the right direction. I need to build an equation by > which correct answers and incorrect answers are tabulated from a sample set > and a value given to the likelihood that a difference can be determined > between two different items. > > > Here is an explanation of the tetrad test. I am trying to create an excel > spread sheet where data can be entered and a value generated indicating > whether the *duplication* is equal to the *control* based on the data > collected from the tetrad Test. > > > Difference Methods Maurice G. O'Sullivan, in A Handbook for Sensory and > Consumer-Driven New Product Development, 2017 > *The Tetrad Test: * > The tetrad method is a difference test involving four samples where the > assessor is presented with blind coded samples with two samples of one > product and two samples of another product. The assessors must then group > the products into two groups according to their similarity. Note that these > instructions are different from asking the subjects to identify the two > most similar samples (Ennis and Rousseau, 2012). The probability of > guessing the right answer is similar to the triangle test (33%). The tetrad > test has also received lots of interest due to its potential to provide > increased power without specification of an attribute. This greater power > means that for the same sample size, an existing difference is less likely > to be missed (Ennis and Jesionka, 2011; Ennis and Rousseau, 2012). The > tetrad method can thus reduce the likelihood of 'alpha' and 'beta' risk > sensory testing errors. Alpha risk is the risk of making a wrong decision. > If p is the decision point, then if p < alpha, then the 'null hypothesis' > is rejected. This is 'rejecting the null hypothesis', also called type I > error and occurs when differences are found between samples when really > there are not any. The opposite can also occur, by not rejecting the null > hypothesis and is called beta risk, or type II error. Here, no differences > are found between samples where differences really exist. Alpha and beta > risks can be reduced by increasing the number of observations or the amount > of data needed to make a decision. See Table 1.1 for sample sizes required > for significant differences. > A considerable advantage of the tetrad test is that far fewer assessors > are required compared to the triangle and duo-trio methods. According > to Ennis and Jesionka (2011), p. 87, assessors would be required to achieve > a significant (P < .05, 90% power, d′ = 1.5) difference between samples for > a duo-trio test, 78 for a triangle but only 25 for a tetrad panel. > Greater power means that smaller sample sizes can be used to achieve the > same performance as the triangle test as the sample sizes required by > the tetrad test are theoretically only one-third that required by the > triangle test (Ennis and Jesionka, 2011; Ennis and Rousseau, 2012). This > could be of great commercial benefit in the saving of time, money and > resources. However, the sensory scientist must determine through comparison > which of the triangle or the tetrad method best suits their products and > processes. > > While I am only attempting a single tetrad Test, here is data collected > from a double tetrad meaning each participant took the test twice. > It is a “double tetrad Test” Fail: > 35 person double tetrad > 0 out of 2 correct: 6 > 1 out of 2 correct: 24 > 2 out of 2 correct: 5 > It’s a fail: > > *Test Results* > Observed *Alpha* > *0.6%* > Observed *Beta* > *49.4%* > > Beta needs to be at most 20% > > Here are two links with further depiction of the tetrad test. > http://www.sensometric.org/Resources/Documents/2012/ > Meeting/Presentations/Ennis_Christensen_2012.pdf > http://www.sciencedirect.com/topics/agricultural-and- > biological-sciences/tetrad-test > > >

**Follow-Ups**:**Re: [Phys-L] Tetrad excel equation***From:*John Denker <jsd@av8n.com>

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