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ISM IAS Merit Calculation Observations

ISM IAS Merit Calculation Observations. June 24, 2010. Summary of Observations. There is no Statistical Evidence that IAS Severity for RO 830-2 Post 2008 is Different from Pre 2008 There is no Statistical Evidence that IAS Severity for RO 830-2 Post 2008 is Different from First 7 Tests

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ISM IAS Merit Calculation Observations

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  1. ISM IAS Merit Calculation Observations June 24, 2010

  2. Summary of Observations • There is no Statistical Evidence that IAS Severity for RO 830-2 Post 2008 is Different from Pre 2008 • There is no Statistical Evidence that IAS Severity for RO 830-2 Post 2008 is Different from First 7 Tests • IAS Merits for 830-2 are Estimated to be Higher Post 2008 • Most Proposed Changes to the Merit System for IAS Turn the Cummins ISM into a Completely Different Test for 830-2 • Statistically Significant Increase in Test Variability • Statistically Significant Increase in IAS merits

  3. Summary of Observations • June 22, 2010 Proposed Changes Turn Candidates with 43<IAS<49 and with Previous Merits>1000 into Automatic Fails • June 22, 2010 Proposed Changes Turn Candidates with 31<IAS<43 and with Previous Merits=1000 into Fails • While it Appears that an Oversight May Have Been Made in the Derivation of IAS Min, Max and Anchor, Oversights and/or Mistakes Cannot be Retroactively Corrected Because Changing the Stake in the Ground Changes the Test • This is True for References and Candidates • It is Permissible to Correct References and Candidates Through the Use of Correction Factors and Severity Adjustments, but Not by Changing Established Targets

  4. Data Analysis • 40 Reference Test Results on RO 830-2 • Statistical Comparisons Must Take Lab into Account • 40 Reference Tests Divided into 3 Time Periods • Time Period 1: First 7 Tests (Pre-Severity Change) • Time Period 2: 18 Test Results Between 7/9/2005-9/6/2007 • Time Period 3: 15 Test Results Between 2/3/2008-5/10/2010 • 3 (5) Merit Proposals Evaluated for IAS • Merits1: Original: 16/27/49 • Merits2: 5/26/2010: 23/27/49 • Merits3: 6/22/2010: 22/31/43 • + 2 Bonus Merit System Evaluations

  5. Analysis Logic • IAS for Time Periods 1 and 2 are Always in Original Merits (Data as Presented in TMC Database) • IAS for Time Period 3 is Calculated Using All 3 Merit Proposals • Test the Null Hypothesis that IAS Merits are Equal for all 3 Time Periods • Merit Proposals in which the Null Hypothesis is Rejected are Indications of Changing the ISM Test for 830-2 • The Conclusion that Merits3 Changes the ISM Test for Candidates with IAS Above 31 is Just a Matter of Logic

  6. Simple Dotplots • Dotplots Do Not Take into Account Lab Effects and are Simply for Observational Purposes • Dotplots Show, Observationally, that the IAS Merits are Increasingly Mild when Moving from Merits1 to Merits2 to Merits3 • This is especially apparent when one considers the first test result, generated in Lab D and way out to the right (mild) in Time Period 1, to be an outlier • Merits4 is not as bad as Merits2 and Merits3 • Merits4: 20/27/49

  7. Statistical Models • IAS Merits = f (Lab, Time Period) • Test HO that All 3 Time Periods Have Equal IAS Severity • Only Time Period 3 is Adjusted by Merit Proposals • Statistical Evidence that Time Period 3 is Different is, Therefore, Not Good News for the Merit Proposal • Statistical Evidence that Time Period 3 has Higher Merits than Time Period 1 or 2 for Merits3 • Statistical Evidence that Time Period 3 has Higher Merits than the Aggregate of Time Periods 1 and 2 for Merits2 • Regression Analysis Attached in Excel File • LSM Results Graphed

  8. Graphs of Least Squares Means • The Least Squares Means for Each Time Period are Plotted for Each Merit System Proposal • Note that there is Only No Statistical Evidence of an Impact on ISM IAS Severity for Merits4 • Merits4 also Represents the Smallest Erosion in Test Precision

  9. What About Another Option, Merits5? • Based on Merits3 • Increase the Max from 43 Back to 49 • Merits5: 22/31/49 • Solves the Problem of Candidates Over 31, BUT • IAS Even More Mild! NOT GOOD

  10. Wait! I Want to Do Something • Sorry, Whatever you do to the Merit System Will Change the Test Severity and Precision from its Original Form

  11. Appendix • Data and Regression Analysis

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