Decision Rule to arrive statement of conformity about a tested products.pptx

It covers the points about decision rule used to derive a statement of conformity pertaining to testing and calibration. It is a main requirements of ISO/IEC 17025.

1. Statement of conformity & Decision rule - An Interpretation of test report - Nataraj Kandeepan

2. AN intro… Statement of conformity: Expressing the conformation of products against an established standard based on test results. Decision rule: a statistical approach of taking decision

3. Terminologies Decision rule: A documented rule that describes how measurement uncertainty will be allocated with regard to accepting or rejecting a product according to its specification and the result of a measurement. Acceptance zone, Rejection zone & Guard band: The decision rule enables a Guard Band, (g) to be calculated which defines an Acceptance zone & Rejection zone . If the measurement result is within the acceptance zone the specifications are met & we can assess compliance. If the measurement result is in the rejection zone we can assess noncompliance. The intersection between these two zones is called the Decision limit

4. Terminologies

5. LIMIT OF Acceptance

6. LIMIT OF Acceptance

7. Correct acceptance & Correct rejection

8. Correct acceptance & Correct rejection – Upper limit case Example 1 – case ii (Correct Acceptance) Let, Specification Upper Permitted Limit = 50 µg/kg (Max) Result = 49.5 µg/kg Expanded Uncertainty (U) = +/- 1 µg/kg (@95% Confidence Level, k = 2)   Standard Uncertainty (u) = Expanded Uncertainty (U)/k = 1/2 = 0.5 µg/kg Guard Band (g) = k (One Tailed t Value @ 95% Confidence Level) x Standard Uncertainty (u) = 1.65 x 0.5 = 0.825 Decision Limit = Specification Upper Permitted Limit – Guard Band = 50 – 0.825 = 49.175 µg/kg Hence, after applying decision rule the result is in rejection zone (Result: Fail)

9. Correct acceptance & Correct rejection – Upper limit case Example 1 – case iii (Correct Rejection) Let, Specification Upper Permitted Limit = 50 µg/kg (Max) Result = 50.5 µg/kg Expanded Uncertainty (U) = +/- 1 µg/kg (@95% Confidence Level, k = 2)   Standard Uncertainty (u) = Expanded Uncertainty (U)/k = 1/2 = 0.5 µg/kg Guard Band (g) = k (One Tailed t Value @ 95% Confidence Level) x Standard Uncertainty (u) = 1.65 x 0.5 = 0.825 Decision Limit = Specification Upper Permitted Limit + Guard Band = 50 + 0.825 = 50.825 µg/kg Hence, after applying decision rule the result is in acceptance zone (Result: Pass)

10. Correct acceptance & Correct rejection – lower limit case

11. Correct acceptance & Correct rejection – lower limit case Example 2 – case ii (Correct Rejection) Let, Specification Lower Permitted Limit = 50 µg/kg (Min) Result = 49.5 µg/kg Expanded Uncertainty (U) = +/- 1 µg/kg (@95% Confidence Level, k = 2)   Standard Uncertainty (u) = Expanded Uncertainty (U)/k = 1/2 = 0.5 µg/kg Guard Band (g) = k (One Tailed t Value @ 95% Confidence Level) x Standard Uncertainty (u) = 1.65 x 0.5 = 0.825 Decision Limit = Specification Lower Permitted Limit – Guard Band = 50 – 0.825 = 49.175 µg/kg Hence, after applying decision rule the result is in acceptance zone (Result: Pass)

12. Correct acceptance & Correct rejection – lower limit case Example 2 – case iii (Correct Acceptance) Let, Specification Lower Permitted Limit = 50 µg/kg (Min) Result = 50.5 µg/kg Expanded Uncertainty (U) = +/- 1 µg/kg (@95% Confidence Level, k = 2)   Standard Uncertainty (u) = Expanded Uncertainty (U)/k = 1/2 = 0.5 µg/kg Guard Band (g) = k (One Tailed t Value @ 95% Confidence Level) x Standard Uncertainty (u) = 1.65 x 0.5 = 0.825 Decision Limit = Specification Lower Permitted Limit +Guard Band = 50 + 0.825 = 50.825 µg/kg Hence, after applying decision rule the result is in rejection zone (Result: Fail)

13. Statement of conformity S. No Test Name Requirement Test Result Rating 1 Protein 200 mg/kg (Min) 250 mg/kg (Uncertainty: +/- 1 mg/kg)   Pass (Clear Pass) 2 Pesticide 50 µg/kg (Max) 49.5 µg/kg (Uncertainty: +/- 1) (Decision Limit After Employed Decision Rule: 49.175 µg/kg)   Fail (Initially Pass After Employing Decision Rule Rating Change Into Fail) 3 Pesticide 50 µg/kg (Max) 50.5 µg/kg (Uncertainty: +/- 1 µg/kg) (Decision Limit After Employed Decision Rule: 50.825 µg/kg)   Pass (Initially Fail After Employing Decision Rule Rating Change Into Pass) 4 Protein 10 mg/kg (Min) 10.5 mg/kg (Uncertainty: +/- 0.5 mg/kg) (Decision Limit After Employed Decision Rule: 10.4125 mg/kg) Pass (Initially Pass After Employing Decision Rule Rating Not Change)