Standard Report: Tetrad Test Results

Standard Report: Tetrad Test Results

Overview

Analysis for the Tetrad data in Compusense uses a one-tailed binomial test.

The formula that you can use in Excel to reproduce the same analysis is as follows:

=1-BINOMDIST(x-1,n,0.3333333333333,TRUE)

Where:
  1. x-1 = number of correct responses minus 1

  2. n = total number of evaluations included in the analysis

Tetrad Analysis Details

The Standard report for Tetrad question data includes the following information:
  1. Number of Evaluations - The number of evaluations included in the report.

  2. Samples - Information about the samples in the test that were included in the report.

  3. Difference Test - This is the default analysis. Change the Alpha value or turn off the Difference Test analysis when generating the report in the Results area.


  4. Similarity Test - Analysis type used in Discrimination tests (Triangle, Tetrad, Same/Different, 3-AFC, Duo-Trio, 2-out-of-5, A-not-A, and Torgerson's) when high confidence is required that the products are perceived the same. This analysis can be used in quality control tests, for example. Turn the Similarity Test analysis on or off when generating the report in the Results area.

The Difference Test



  1. Chance. Probability of panelists correctly selecting the odd sample by chance.

  2. N. Total number of evaluations included in the report.

  3. Correct. Count of correct responses.

  4. Incorrect. Count of incorrect responses.

  5. d' (read d prime). The measure of the extent of the overlap of panelist perception. It is the distance between the means of the two distributions measured in terms of their standard deviation.

    The larger the d’ value, the products are more different. Where the d' value is 0 it means that the products are indistinguishable. A d’ of 1 or less might be considered small and a d’ of 2 or more might be considered large, but it depends on various factors.

    This calculation is always done treating each response as independent, as if the test is unreplicated. For example, d' on a back-to-back test with 50 assessors who provide 2 responses, calculation is done as if there are 100 assessors who provide 1 response each.

  6. p-value. The probability of observing an outcome that is more extreme than or equal to the test statistic observed assuming that the null hypothesis is true.

  7. Significant at an Alpha level. Indicator whether there is a significant difference between samples at the specified level of significance (Alpha). The default Alpha value is 0.05, but it can be changed in the results area when generating the report.


  8. Tetrad test number. Our example with numbered bubbles shows that a back to back Tetrad was ran on two samples. Below is an example of a back to back Tetrad analysis for four samples.


  9. Pooled. In the analysis where two samples (see the Samples table in our example above) were evaluated back to back, the N is increased by multiplying the actual N by the number of tests. Each test is treated as done by different panelists even though they were seen back to back by the same panelists. Pooled analysis is not available in single tests and in any other variation of back to back tests (e.g. more than two tests on two samples, or more than two sample tests).

  10. Both Tetrads. In a back to back Tetrad analysis (true replicate of two samples), you can see how many panelists answered both Tetrad tests correctly. The probability of panelists correctly sorting the samples for both tests by chance decreases. Both Tetrads analysis is not available in single tests and in any other variation of back to back tests (e.g. more than two tests on two samples, or more than two sample tests).

The Similarity Test



  1. N. Total number of evaluations included in the report.

  2. Correct. Count of correct responses (where the odd sample was identified correctly).

  3. Responses Required. Number of correct responses required to reach a conclusion of Not Similar.

  4. Conclusion. When the number of correct responses is smaller than the responses required, the samples are deemed similar. When the number of correct responses is equal to or greater than the responses required, the samples are deemed not similar.

  5. Pc(estimate). Proportion correct.

    Formula: Pc = c / n

    Where:
    c = number of correct responses.

    n = total number of evaluations.

  6. Pd(estimate). Proportion of distinguishers.

    Formula: Pd = (Pc - Pg) / (1 - Pg)

    Where:
    Pc = proportion correct.

    Pg = guessing probability.

  7. Std error (Pd). Standard error of the estimate of the proportion of (momentary) discriminators.

    Formula: (1 / (1 - Pg)) * sqrt(Pc * (1 - Pc) / n)

    Where:
    Pg = guessing probability.

    sqrt = square root.

    Pc = proportion correct.

  8. Pmin, Lower confidence limit (α=0.2).

    Formula: Pmin = Pd + Zalpha * Std error (Pd)

    Where:
    Pd = proportion of distinguishers.

    Zalpha = Alpha value. The default Alpha value is 0.10, but it can be changed in the Defaults or in the results area.

    Std error (Pd) =Standard error of the estimate of the proportion of (momentary) discriminators.

  9. Pmax, Upper confidence limit (β=0.01).

    Formula: Pmax = Pd + Zbeta * Std error (Pd)

    Where:
    Pd = proportion of distinguishers.

    Zbeta = Beta value. The default Beta value is 0.10, but it can be changed in the Defaults or in the results area.

    Std error (Pd) =Standard error of the estimate of the proportion of (momentary) discriminators.

  10. Tetrad test number. Our example with numbered bubbles shows that a back to back Tetrad was ran on two samples. Below is an example of a back to back Tetrad analysis for four samples.


  11. Pooled. In the analysis where two samples were evaluated back to back, the N is increased by multiplying the actual N by the number of tests. Each test is treated as done by different panelists even though they were seen back to back by the same panelists. Pooled analysis is not available in single tests and in any other variation of back to back tests (e.g. more than two tests on two samples, or more than two sample tests).

  12. Both Tetrads. In a back to back Tetrad analysis (true replicate of two samples), you can see how many panelists answered both Tetrad tests correctly. The probability of panelists correctly sorting the samples for both tests by chance decreases. Both Tetrads analysis is not available in single tests and in any other variation of back to back tests (e.g. more than two tests on two samples, or more than two sample tests).


Additional Tetrad Analysis

If your test included a follow up Tetrad related Comment or a Tetrad related Choose question, your Standard report will provide you with Tetrad related Comments or Tetrad related Choose data, depending on what question type you added into your test. Let's review what each follow up question provides in the Standard report.

When Tetrad related comments are collected, the analysis will separate the panelists' comments based on their correct and incorrect Tetrad responses. In our example below, we can see that the panelist #5 correctly evaluated both Tetrads and his or her comments for both tests are in the table labeled Correct response related comments.

The Incorrect response related comments table displays the comments for all the incorrect Tetrad responses. Our example does not have any comments in it because our example test was set up with connections. The connections did not allow panelists who answered the Tetrad incorrectly to comment, however, the table still shows individual panelists and the Tetrad test # that they did not evaluate correctly.


When a Tetrad related Choose data is collected, the analysis will display the Crosstabulation and Percentage Crosstabulation tables based on panelists' correct and incorrect Tetrad responses.

  1. Count of choice selections for correct Tetrad responses.

  2. Count of choice selections for incorrect Tetrad responses.
To change the Crosstabulation format, when generating the Standard report in the Results area, expand Select options and choose what works best for your analysis needs.


Panelist Performance Report

Run a Panelist Performance report in the Panelists library to see how your panelists have performed over multiple Tetrad tests over time, allowing you to discover patterns or non-differentiators. The workflow for the report will be available soon.



Data

You can use the Data tab for another quick and easy insight into panelist performance within a single test (rather than across multiple tests as described above). The example screenshot below was taken in a test that had a back to back Tetrad scenario where two different samples were evaluated in each Tetrad (4 samples in total).



Graphs

The data from single and back to back Tetrads with two products can also be graphed. To generate the graph:
  1. In the Results area, click the Graphs tab.

  2. In the left sliding pane, select the Tetrad question.

  3. Update any of the parameters in the right sliding pane.
Graphs cannot be generated on Tetrad related comment and CATA questions, and on back-to-back Tetrads with 4 or more products.




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