gsr 2005 copenhagen uhlig public · 8 pt gsr 2005 –statisticalresultspt gsr 2005...

Proficiency Test: Gun Shot Residues 2005Proficiency Test: Gun Shot Residues 2005

Statistical analysis of the results

PD Dr. Steffen Uhlig

Statistical analysis of the results

PD Dr. Steffen Uhlig

May 2005

22 PT GSR 2005 – Statistical resultsPT GSR 2005 – Statistical results

quo data provides scientific services for establishing measurement methods and quality assurance� Interlaboratory studies

� In-house studies

� Optimisation projects

� Development of validation criteria

� Training and workshops

quo data provides software� for interlaboratory studies

� for in-house validation

� for the optimization of measurement methods

� ...

quo data develops workstations for the analysis of organic compounds� ELISA

� Yeast assays

Products and services of quo dataProducts and services of quo data

quo data: productsand services

Method assessment

Laboratory assessment

System assessment


Method assessment


System assessment


Method assessment

1. Standard Deviation of Particle Number

2. Method detection capability


Method assessment


System assessment


Method assessment


System assessment


Standard Deviation of Particle Number

• Target value = no. of particles per size class – 1

• Standard deviation of the number of correctly detected particles according to DIN 38302 A 45 = CD ISO 20 612

(ProLab 2006):

⇒ Robust statistical method (outlier resistant), hence nooutlier elimination necessary

⇒ Classical statistical requirement such as normaldistribution assumption not required

⇒ Specifically developed for asymmetrical and discrete distributions


Method assessment


System assessment


Method assessment


System assessment


Standard Deviation of Particle Numbers

total no.

of part.

ref. s.d. s.d.

target

s.d.

on

sample

X empirical (10% of

reference

X)

used

1.2µm + 56 55 3.1 5.5 3.1

0.8µm +86 85 6.7 8.5 6.7

2.4µm24 23 1.1 2.3 1.1

1.2µm32 31 3 3.1 3

0.8µm30 29 3.8 2.9 2.9

0.5µm14 13 4.6 1.3 1.3

measure-

ment charac-

teristics

SPS-5P-2A/B/C quo data: productsand services

Method assessment


System assessment


Method assessment


System assessment


Method detection capability

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3

Particle Size [µm]

Dete

cti

on

cap

ab

ilit

y

identified detected

Probability to identify or to detect a particle (lab selected by random)

90% detection capability: 1.5µm90% identification capability: 1.6µm

1 µm particles will be detected (identified) with a probability of approx. 79% (76%).


Method assessment


System assessment


Method assessment


System assessment


assessment of the detection capabilities

Probability for correctly detected particles in GSR2005, GSR2003 and including only participants from both interlaboratory studies

90% detection capability2003: 1.8 µm2005: 1.5 µm

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3

Particle Size [µm]

Dete

cti

on

cap

ab

ilit

y

2005 2003 2005 only with participants from 2003


Method assessment


System assessment


Method assessment


System assessment



1. Z Scores

2. Method detection capability

3. Indicative and false positive results


Method assessment


System assessment


Method assessment


System assessment


Z Scores

Z scores of count of correctly detected particles (Part 1)(standardized deviations from target)

|Z| > 3, 2 < |Z| ≤ 3, |Z| ≤ 2

-3 0 3 -3 0 3 -3 0 3 -3 0 3 -3 0 3 -3 0 3

COP05 COP08 COP12 COP24 COPG08 COPG12010_1010_2

011012013014015016017019

021_2021_6021_8

110111112113114

115_1115_2

117118119120122123124310311312313314315316317319320321410411412

-2,308-2,308

-2,308-2,308

-2,308-2,308

-2,308-2,308

-2,759-2,759

-2,414-2,414

-2,069-2,069

-2,069-2,069

-2,699-2,699

-2,791-2,791

-2,791-2,791

-2,819-2,819

-2,374-2,374

-2,226-2,226

-2,904-2,904

-2,259-2,259

-6,923-6,923

-3,846-3,846

-10,000-10,000

-10,000-10,000

-6,923-6,923

-3,077-3,077

-3,077-3,077-6,923-6,923

-10,000-10,000

-4,615-4,615

-10,000-10,000-8,462-8,462

-4,615-4,615

-10,000-10,000

-10,000-10,000

-6,154-6,154

-10,000-10,000

-8,462-8,462

-6,154-6,154

-10,000-10,000

-4,138-4,138

-10,000-10,000

-5,862-5,862

-8,276-8,276

-10,000-10,000

-10,000-10,000

-6,897-6,897

-9,784-9,784

-3,374-3,374

-9,784-9,784

-4,652-4,652

-4,652-4,652

-9,199-9,199

-6,825-6,825

-5,045-5,045

-5,193-5,193

-9,347-9,347

-3,116-3,116

-10,326-10,326

-5,163-5,163

-3,227-3,227

-10,649-10,649


Method assessment


System assessment


Method assessment


System assessment


Z Scores

Z scores of count of correctly detected particles (Part 2)(standardized deviations from target)

|Z| > 3, 2 < |Z| ≤ 3, |Z| ≤ 2

-3 0 3 -3 0 3 -3 0 3 -3 0 3 -3 0 3 -3 0 3

COP05 COP08 COP12 COP24 COPG08 COPG12413414415416417418

419_1419_2

420421422423610611612614

615_1615_2616_1616_2

617619620

621_1621_2

710711712713714716717718719720721722723724725726727

-2,759-2,759

-2,699-2,699

-2,362-2,362

-2,024-2,024

-2,791-2,791

-2,581-2,581

-7,692-7,692-10,000-10,000

-10,000-10,000

-3,846-3,846

-3,846-3,846

-6,923-6,923-3,077-3,077-10,000-10,000

-10,000-10,000

-10,000-10,000

-10,000-10,000

-5,385-5,385

-5,517-5,517

-10,000-10,000

-4,138-4,138

-10,000-10,000

-8,966-8,966

-10,000-10,000

-9,655-9,655

-10,000-10,000

-10,000-10,000

-5,398-5,398

-3,711-3,711

-10,458-10,458-4,386-4,386

-8,771-8,771

-10,458-10,458

-3,711-3,711

-6,073-6,073

-7,759-7,759

-3,722-3,722

-4,652-4,652

-10,235-10,235

-4,451-4,451

-5,341-5,341

-4,006-4,006

-9,051-9,051-4,154-4,154

-9,644-9,644

-9,199-9,199

-6,528-6,528

-7,270-7,270

-7,864-7,864

-5,163-5,163

-4,195-4,195

-4,518-4,518

-10,003-10,003-6,131-6,131

-12,262-12,262

-10,326-10,326

-4,840-4,840

-6,131-6,131

-7,422-7,422


Method assessment


System assessment


Method assessment


System assessment


Classification of Z scores

Sat is-

factory

Quest io-

nable

Unsat is-

factory

(|z| < 2) (2 < |z| < 3) (|z| > 3)

1.2µm+ 64 (79%) 3 (4%) 14 (17%)

0.8µm+ 51 (74%) 3 (4%) 15 (22%)

2.4µm 75 (90%) 3 (4%) 5 ( 6%)

1.2µm 65 (80%) 3 (4%) 12 (15%)

0.8µm 49 (69%) 5 (7%) 17 (24%)

0.5µm 26 (43%) 4 (7%) 31 (51%)


Method assessment


System assessment


Method assessment


System assessment


Enclosure to the certificate of participation

Description

True

value

Assigned

value*

Lab

result** s.d. used Z score

Count of 0.5 µµµµm particles

correctly detected 14 13 4 1.3 -6.9


correctly detected 30 29 26 2.9 -1


correctly detected 32 31 31 3 0


correctly detected 24 23 23 1.1 0

Count of particles ≥ 0.8 µµµµm

correctly detected 86 85 82 8.5 -0.4

Count of particles ≥ 1.2 µµµµm

correctly detected 56 55 55 3.2 0


Method assessment


System assessment


Method assessment


System assessment


Detection capability per participant

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3

50% - Percentile: m50 = 0.6 µm;

90% - Percentile: m90 = 0.8 µm;

steepness:s = -6

s

m

+

=

50

Size Particle1

1cap.detection

Particle size (µm)


Method assessment


System assessment


Method assessment


System assessment


Atypical detection capability curves

s

m

+

=

50

Size Particle1

1cap.detection

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3

Detectionprobability not converging to 100%.

Problems with plate?


Method assessment


System assessment


Method assessment


System assessment



s

m

+

=

50

Size Particle1

1cap.detection

Detection probability not depending on particle size?

Problems with plate?

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3


Method assessment


System assessment


Method assessment


System assessment



All particles detected; percentiles cannot be calculated.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3


Method assessment


System assessment


Method assessment


System assessment



Low detection capability and low increase for larger particle size.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.5 1 1.5 2 2.5 3


Method assessment


System assessment


Method assessment


System assessment

gsr 2005 copenhagen uhlig public · 8 pt gsr 2005 –statisticalresultspt gsr 2005...

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