First lab managers’ meeting of the South-East Asia Laboratory NETwork (SEALNET 2.0) - Quality improvement in Asian soil laboratories: towards standardization and harmonization of soil analyses and their interpretation, Bogor, Indonesia, 20 - 24 November 2017.

1. Mr. Christian Hartmann, IRD
Mrs. Nopmanee Suvannang, LDD
First Meeting of the GLOSOLAN, FAO Headquarters, Rome, 1-2 Nov 2017
1
MEASURING DATA QUALITY

2. 2
Precision Accuracy Safety

3. It is important to reach
the highest step….
It is also important to help
each other to reach
the highest step!

4. 4
DEFINITIONS & CONCEPTS
RESULT:
TRUE VALUE, MISTAKE, ERROR, UNCERTAINTY,
PRECISION, ACCURACY....

5. 5
DEFINITIONS & CONCEPTS
RESULT:
TRUE VALUE, MISTAKE, ERROR, UNCERTAINTY,
PRECISION, ACCURACY....
not only ideas but also DATA

6. 6
For analytical testing:
impossible to make an exact measurement
because you will ALWAYS have errors.
A good result will only be
as close as possible
from the true value.
(errors ≠ mistakes)

7. 7
Errors can NEVER be avoided:
1.4 !

8. 8
1.4 ! ≠ 1.4 !
Errors can NEVER be avoided:
errors are a part of the measures.

9. 9
Errors can NEVER be avoided:
errors are a part of the measures.

10. 10
Errors can NEVER be avoided:
errors are a part of yours measures.

11. 11
Error ≠ uncertainty !!!!!!

12. 12
Error ≠ uncertainty:
error:
1. exists for each measure but...

13. 13
Error ≠ uncertainty:
error:
1. exists for each measure but...
2. you ignore how much it is
(you cannot know the ‘true‘ value)

14. 14
uncertainty:
1.concerns a set of measurements
error:
1. exists for each measure but...
2. you ignore how much it is
(you cannot know the ‘true‘ value)
Error ≠ uncertainty:

15. 15
uncertainty:
1. concerns a set of measurements
2. you can estimate it!
==>mean value & standard deviation…
error:
1. exists for each measure but...
2. you ignore how much it is
(you cannot know the ‘true‘ value)
Error ≠ uncertainty:

16. 16

17. 17
4.1
4.1
4.2
4.0
4.1
4.1
4.3
4.1

18. 18
4.1
4.1
4.2
4.0
4.1
4.1
4.3
4.1

19. 19
4.1
4.1
4.2
4.0
4.1
4.1
4.3
4.1

20. 20
s = 0.082 rounded
s = 0.1
4.1
4.1
4.2
4.0
4.1
4.1
4.3
4.1
sd = 0.1

21. plot your results on a:
Levey-Jennings (LV) chart

22. 22
Levey-Jennings (LV) chart
4.4
4.3
4.2
4.1
4.0
3.9
3.8

23. 23
Levey-Jennings (LV) chart
sd = 0.1

24. 24
the perfect tool for quality control!
Levey-Jennings (LV) chart

25. 25
Levey-Jennings (LV) chart
remember the previous presentation….

26. Analytical errors can be of 2 categories:
1.Random or ‘unpredictable’ deviations between
replicates

27. 27
Levey-Jennings (LV) chart

28. 28
Levey-Jennings (LV) chart

29. 29
Levey-Jennings chart:
visualise the quality of your results…

30. 30
Levey-Jennings chart:
visualise the quality of your results…

31. 31
and so what?
I cannot replicate several times all my analysis,
how can I know the quality of my results!

32. 32
and so what?
I cannot replicate several times all my analysis,
how can I know the quality of my results!
replicate your analysis on your
INTERNAL CONTROL SAMPLES!

33. 33
Collect 10 to 100 kg of soils that
represent soils you will analyse.
Air dry,
but not under direct sunlight.
Crush and sieve at 2 mm, store
in smaller container (1 or 2 kg).

34. 34
Include your control sample
in the analytical batches:
1 /10?

35. 35
Include your control sample
in the analytical batches:
1 /10?

36. plot the results of
control samples on a
Levey-Jennings (LV) chart

37. 37

38. 38
UCL = Upper Control Limit (or Upper Action Limit).
LCL = Lower Control Limit (or Lower Action Limit). UWL = Upper
Warning Limit. LWL = Lower Warning Limit.
+2 SD
Action limit
Warning Limit
+3 SD
-2 SD
-3 SD

39. 39
Action limit
Warning Limit

40. 40
UCL = Upper Control Limit (or Upper Action Limit).
LCL = Lower Control Limit (or Lower Action Limit). UWL = Upper
Warning Limit. LWL = Lower Warning Limit.
+2 SD
Action limit
Warning Limit
+3 SD
-2 SD
-3 SD

41. 41
your internal control sample
is an indicator of the quality of
the results for all samples in the batch

42. 42
based on these results decide:
1. if you accept/reject
all results of this batch.
2. where the error come from.
your internal control sample
is an indicator of the quality of
the results for all samples in the batch

43. 43
Different paterns:

44. 44

45. 45
Interpreting the different paterns
is a diagnosis, it depends on the skill
of the person who look at it.
This is discussed during meetings of
lab managers but also propositions
from private companies…

46. 46

47. 47

48. 48

49. 49

50. 50

51. 51

52. 52

53. 53
BIAS !!!

54. 54
BIAS !!!
Data systematically on the same side

55. 55

56. 56

57. 57
They are many more rules…
But for SEALNET the main point is
not to ‘reject/accept’….

58. 58
They are many more rules…
But for SEALNET the main point is
not to ‘reject/accept’….
The main points are:
1.helping measuring your quality
2.helping you to increase your Q.

59. 59
plot the results of your internal
controls samples is:
absolutely crucial!
if you don’t do, it is like driving
a car with closed eyes…

60. 60
III –
INTERNAL QUALITY CONTROL (QC).
Reminder:
Quality control in the soil laboratory:
a statistical process
to monitor and evaluate
the analytical process & results’ quality.

61. 61
III –
INTERNAL QUALITY CONTROL (QC).
Reminder:
Quality control in the soil laboratory:
a statistical process
to monitor and evaluate
the analytical process & results’ quality.
Statistics are sometimes boring, isn’t it?

62. to reach the goal, we’ll help each others…

63. 63

64. Thanks for your attention
First Meeting of the GLOSOLAN, FAO
Headquarters, Rome, 1-2 Nov 2017
64