Objective Scoring System – version 3
by Raymond Nelson, Mark Handler, and Donald Krapohl
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Poster #2 - Validation with mixed format field investigation polygraphs
Poster #3 - Additional validation with LEPET and PCSOT screening exams
The OSS-3 Report
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How to read the OSS-3 Report


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There are six main sections in the OSS-3 report, the six sections are listed below and shown highlighted in red below.
  1. Results
  2. Details
  3. Questions
  4. Measurements
  5. Standardized Lognormal Ratios
  6. Remarks

OSS3 Walk Through
OSS3 Report

Section 1 – Reading the results

In the results section you will be given the test result, and p-value, or level of significance, for that result, along with information about the type of test technique and the decision rules used to score the test.

The OSS-3 algorithm regards all variants of Zone techniques as single issue examinations in which it is inconceivable that a test subject could lie to one or more test questions while being truthful to other questions regarding involvement in a single known issue.

All variants of the MGQT format are regarded by the OSS-3 algorithm as multiple facet examinations, in which it is theoretically conceivable that a test subject could lie to one or more questions while being truthful to other questions about various forms of involvement in a single known issue. The OSS-3 algorithm does not make truthful and deceptive classifications simultaneously, and any indication of significant reactions to any test question precludes the possibility of a truthful classification for all other questions.

Screening examinations, for risk assessment or compliance monitoring, are regarded by the OSS-3 algorithm as mixed-issues examinations in which it is conceivable that a test subject could lie to one or more test questions while being truthful to other questions about involvement in several distinct unknown issues (for which there is no known allegation). Again, the OSS-3 algorithm does not make truthful and deceptive classifications simultaneously, and any indication of significant reactions to any test question precludes the possibility of a truthful classification for all other questions.

By default, the OSS-3 algorithm will score all variants the Zone and MGQT techniques using the OSS-3/Senter algorithm which uses two-stage rules (Senter and Dollins, 2003; Senter, 2003) that have been shown to provide optimal classification accuracy, including optimum sensitivity to deception, balanced accuracy, and minimal inconclusive classifications.

Screening exams are scored using the OSS-3/Screening algorithm which is optimized to maximize sensitivity to deception when scoring multiple distinct/mixed question targets, and uses an omnibus test of between question variance to reduce inconclusive classifications of test data that cannot be classified as deceptive. 

Truthful results, reported as “No Significant Reactions,” occur when the observed p-value indicates a statistically significant difference between the observed numerical score and that expected from deceptive test subjects, using normative data obtained through bootstrap training with the confirmed single issue examinations from the development sample. 

Deceptive results, in which an observed p-value indicates a statistically significant difference between the observed numerical score and that expected from truthful persons, and are reported as “Significant Reactions.” 

When the observed p-value fails to meet decision alpha thresholds for truthful or deceptive classification the test result will be reported as “Inconclusive.” No opinion can be rendered regarding those results.

The OSS-3 algorithm regards the measurable presence or absence of reactions, and observed mathematical significance, as unequivocal according to the specified decision alpha level. Professional opinons about deception or truthfulness are made by field examiners according to professional standards of practice, training, and agency policies regarding tollerance for risk or error.

The p-value for truthful results can be thought of as the estimated proportion of deceptive persons that might produce a numerical score of equal or greater magnitude, (obtained as the mathematical mean of the combined weighted means of standardized lognormal R/Cmean  ratios). The p-value for truthful results may also be thought of as the probability that a test result was produced by a deceptive person, or the probability that a test result is produced by chance or error. Conversely, p-values for deceptive classifications can be thought of as the estimated proportion of truthful  persons that might produce a numerical score of equal or greater magnitude. P-values for deceptive results may also be though of as the probability that a test result was produced by a truthful person, or the probability that a test result was produced by chance or error. Users of the OSS-3 computer scoring algorithm should remain aware that it would be a theoretically incorrect over-simplification to attempt to describe a p-value as a probability of deception or truthfulness

OSS3 Walk Through
Section 1 Results

Section 2 – Looking at the details

In the details section you will find four subsections: test details, spot scores, decision alpha, and the component weights.

The test details consist of the names of the Examinee and Examiner, in addition to the examination date and date on which the examination was scored with the OSS-3 computerized scoring algorithm.

Because numerical scores are aggregated through the mathematical mean of the combined weighted mean of component scores, and not through simple cumulation, the range of scale for individual questions is identical to the range of scale for the  aggregated  numerical scores (grand mean). P-values for individual questions are therefore calculated in the same manner as the p-value for the overall score. Classification results for individual questions are provided on the OSS-3 report for multiple-facet and mixed-issues examinations. For event-specific/single-issue examinations, the individual question stimuli are assumed to be logically synonymous and are not included in the examination report.

Other information in the detail session may be of interest to an examiner, auditor, or quality assurance reviewer, and include the component contribution or weighting, and the specified decision decision alpha thresholds at which deceptive and truthful classifications are permitted. Also included is information about the use of a Bonferonni correction to the potential for inflated alpha levels with multiple-facet and single issue exams when using two-stage or spot scoring rules.

OSS3 Walk Through
Section 2 Details

Section 3 – Reviewing the questions

The questions section will list the actual relevant question targets from the in-test phase of the examination. The OSS-3 computerized scoring algorithm can score examination techniques consisting of two to four relevant questions.

OSS3 Walk Through
Section 3 Questions

Section 4 – Verifying the measurements

The measurement section displays all of the physiological measurements that were obtained for the scoring algorithm.  The measurements are separated into separate matrices for each test chart, with each row of each matrix containing the measurement data for a single component. The OSS-3 algorithm is designed to score examinations consisting of three to five test charts, and will not score examinations for which there are fewer than three test charts. Questions themselves are aligned vertically between the matrices for the three to five test charts. Measurements that were previously marked as artifacts are not included in the mathematical analysis, and are identifiable by the text value appended to the beginning of the numeric measurement. Measurements that have been edited prior to analysis are also easily identified by the “&”  within the numeric string composed of the original and edited measurements. In this way the original measurement value is retained for auditing purposes, and edited measurement values are easily identified in the OSS-3 report. The OSS-3 algorithm does not use measurement values that would result from descending EDA or cardio tracings. Negative measurement values are replaced with the value zero (0) at the time of measurement. Zero values in the measurement table alert the examiner or reviewer that a tracing segment was descending and un-interpretable at the time of the question stimulus.

 

OSS3 Walk Through
Section 4 Measurements

Section 5 – Understanding the Lognormal ratios

Standardized lognormal ratios are the final result of the mathematical transformation and aggregation of the Kircher measurements. Transformations begin with the calculation of R/Cmean ratio, using the mean comparison values within each component. In order to accommodate polygraph techniques with two to four target questions and three to five test charts, it is necessary to plan for the aggregation of data through averaging instead of cumulative totals.

Because the calculation of R/Cmean ratios creates an asymmetrical distribution of possible data values, with lognormal distribution shape, consisting of all possible positive real numbers with a mean of one (1), averaging is not appropriate without some initial transformation of the data. Transformation of the asymmetrical R/Cmean ratios to their natural logarithms results in a symmetrical distribution of positive and negative real numbers with a mean of zero, which can be averaged without introducing mathematical bias to the data. Lognormal values are standardized per each component, using normative data (means and standard deviations) obtained through bootstrap re-sampling of the training sample. 

Standardized lognormal R/Cmean ratios are presented on the OSS-3 report, and the component values are further combined through weighted averaging for each iteration of each relevant stimulus, using the component weights that are indicated in the details section of the OSS-3 report. Those weighted mean values are then combined, through the mathematical mean of each of the relevant stimuli, between the three to five test charts. Mean values for the two to four relevant questions are further averaged to achieve a grand mean score that is compared to the cumulative normal distributions for confirmed truthful and confirmed deceptive cases, using normative data that was obtained through  bootstrap resampling. When using two-stage, spot scoring, or screening rules, mean values for each of the individual relevant stimuli are also compared to the cumulative normal distribution for truthful subjects using the specified decision alpha for deceptive classifications.

In addition to the standardized lognormal R/Cmean ratios, the OSS-3 report displays the mathematical mean of the weighted means of the lognormal  R/Cmean ratios for each of the test stimulus targets, along with the grand mean score for the combined stimulus questions.

OSS3 Walk Through
Section 5 Lognormal Ratios

Section 6 – Reading the remarks

The remarks section will display any remarks entered by the examiner during or after the examination. Extrapolygraphic information, that may affect the interpretation of a test, should be entered into the remarks section, including information about health, medications, mental status, non-cooperation and attitudinal information might be useful to include in this field. Alternatively the remarks section may be used to display information obtained from the examinee during the post-test review.

 

OSS3 Walk Through
Section 5 Remarks

 

Summary

The OSS-3 report summarizes all critical  information used to achieve the test result, including  information about the advanced user settings of the OSS-3 algorithm, along with auditing information regarding the examiner's review or editing of the raw data from the automated physiological measurements.

Disclaimer: The OSS-3 developers have provided the scoring algorithm without any warranties or assurances. All use of the OSS-3 computerized polygraph scoring algorithm in whole or part is done with the understanding that it is the examiners responsibility, at the time of the examination, to assure that the examinee's truthfulness or deception is the sole cause for the presence or absence of significant reactions. Just as legal evidence is not itself a legal finding of fact, which is the role always of judges and juries, it is an ethical axiom in testing sciences that tests themselves do not make decisions but provide information to the professionals who use tests. Decisions are always made by professionals, who are trained and authorized to use test data and other information as a basis for professional opinion. Decisions, and decision thresholds are sometimes necessarily influenced by  matters of administrative policy. While every effort has been made to design and validate a scoring algorithm with maximum field utility and maximum classification accuracy, effective use of the OSS-3 algorithm in field settings depends in large part on a properly administered examination. It is the responsibility of each professional to become familiar with the empirical methods and principles underlying any test method and scoring paradigm, including its strengths and limitations, and to use testing information according to one's level of competence, training, and established policies.  Installation and use of the OSS-3 algorithm signifies the users agreement to indemnify the developers against any and all forms of liability associated with its use or misuse.