R-Index

R-Index

Introduction

The R-index is a tool in sensory science that helps quantify the difference between two samples. The R-index is designed to quantify the area under an empirical Receiver Operating Characteristics (ROC) curve within the framework of signal detection theory.
This index is determined through rating or ranking tasks, where panellists decide if a sample is a signal or noise. In rating tasks, panelists choose from categories like "signal sure" or "noise sure," while ranking tasks involve comparing samples based on signal strength. Typically, the sample with lower intensity is considered "noise," and the one with higher intensity is seen as the "signal."

Template Description

R-Index

The template starts with a screen, which can be used to welcome the panellists. In the design section, the first screen has instructions, followed by a second screen in which two questionnaires are added:
Category Question: panellists are asked to specify the degree of certainty with which they believe the sample tested is the reference sample or not. 
Remark Question: panellists are free to provide more details about their selection, such as the direction of the difference. 
On the end screen, the template incorporates a thank-you message, providing an opportunity for you to personalize a final message for the panellists. 
Within the design settings, you can examine how each panellist will receive the sample, with each set corresponding to a specific order of presentation for an individual panellist.
Three products are shown in this template in a monadic sequential order. To modify the quantity of products included in your test, select Generate Design. 

R-Index Ranked

The template starts with a screen, which can be used to welcome the panellists. In the design section, there is one screen on which two questionnaires are added:
Ranking Question: panellists are asked to rank the intensity of an attribute on a scale of low to high after being shown all the products included in the design. 
Remark Question: panellists are free to provide more details about their selection.
On the end screen, the template incorporates a thank-you message, providing an opportunity for you to personalize a final message for the panellists. 
In the design settings, you can review how each panellist will receive the sample, with each set corresponding to a specific order of presentation. The design has been created as a block design, which means the panellist will receive all the products simultaneously. Within the design creator, you can adjust the amount/number of samples and blocks (combinations). 
You have the flexibility to edit the product properties by clicking on the Product section.

Raw Data Representation

R-Index

The raw data will be displayed with each row corresponding to a product evaluated by a judge (panellist), followed by the outcome of the R-Index question type. 

R-Index Ranked

The raw data will be displayed, with each row corresponding to an individual judge and the product they were presented with. In the Q1 or R-Index column, you can see the number in which place the panellist ranked that specific product. When the comment question was added to the project, you can see the comments of the panellist in the Q2 column.  

Analysis

If the data has been gathered with the R-Index template, you can access EyeOpenR and navigate to the Discrimination methods. Choose the R-Index analysis to examine your results. 
If the data has been gathered with the R-Index Ranked template, you can  access EyeOpenR and navigate to the Ranking methods. Choose the R-Index Ranked analysis to examine your results.
Additional details about this analysis can be found in the following article: https://support.eyequestion.nl/portal/en/kb/articles/r-index-analysis

References

  1. John Brown (Brown J. 1974. Recognition assessed by rating and ranking. Br. J. Psychol.65, 13–22.)

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