How to best assess repeatability of a variable performed in triplicate

[james campling]

Hi all, thanks in advance for any help offered here

This relates to my medical dissertation for the pathology college

I compared one analyte (HPC) to the current gold standard. As this was a new test the new analyte was run in triplicate for the first 6 months. Thus I have 196 triplicate results

I wish to statistically assess the repeatability of this analyte

When I wrote this up the first time I used a pooled repeatability standard deviation using the following: - pooled repeatability standard deviation (SD) was calculated as √ (∑WV) / (∑DOF) where WV = weighted variance and DOF = Degrees of freedom. The weighted variance for each data = Degrees of freedom x SD². Degrees of freedom of n – 1 = 2 was used.

This was quite significantly over my head in terms of statistical knowledge at the time

Can others suggest in stata how I might best approach this situation to assess overall repeatability of the test

Kind Regards

Jamie

[james campling]

Just as an add on and apologies I should have done this in the first instance but new at this. Have tried to follow some code on ICC and concordance correlation. I don't think either are really applicable to my dataset but it did help me arrange my data into long version which is as follows. I have 27 triplicate results from the analyser (each single test performed in triplicate immediately under the same conditions . I want to assess the repeatability of the analyser.


+-------------------------------------------------------------+
| Test result1 result2 result3 E id Time Result |
|-------------------------------------------------------------|
1. | 1 5 8 8 . 1 1 5 |
2. | 2 3 4 3 . 1 2 8 |
3. | 3 5 5 2 . 1 3 8 |
4. | 4 23 22 19 . 2 1 3 |
|-------------------------------------------------------------|
5. | 5 142 140 137 . 2 2 4 |
6. | 6 12 3 7 . 2 3 3 |
7. | 7 14 14 11 . 3 1 5 |
8. | 8 21 20 24 . 3 2 5 |
|-------------------------------------------------------------|
9. | 9 32 36 34 . 3 3 2 |
10. | 10 19 14 19 . 4 1 23 |
11. | 11 6 5 5 . 4 2 22 |
12. | 12 4 4 11 . 4 3 19 |
|-------------------------------------------------------------|
13. | 13 20 17 14 . 5 1 142 |
14. | 14 2 10 10 . 5 2 140 |
15. | 15 4 5 5 . 5 3 137 |
16. | 16 15 10 7 . 6 1 12 |
|-------------------------------------------------------------|
17. | 17 5 5 5 . 6 2 3 |
18. | 18 38 27 25 . 6 3 7 |
19. | 19 19 18 25 . 7 1 14 |
20. | 20 2 4 4 . 7 2 14 |
|-------------------------------------------------------------|
21. | 21 6 6 7 . 7 3 11 |
22. | 22 11 18 21 . 8 1 21 |
23. | 23 24 17 17 . 8 2 20 |
24. | 24 10 7 8 . 8 3 24 |
|-------------------------------------------------------------|
25. | 25 23 16 11 . 9 1 32 |
26. | 26 50 45 44 . 9 2 36 |
27. | 27 37 31 33 . 9 3 34 |
28. | . . . . . 10 1 19 |
|-------------------------------------------------------------|
29. | . . . . . 10 2 14 |
30. | . . . . . 10 3 19 |
31. | . . . . . 11 1 6 |
32. | . . . . . 11 2 5 |
|-------------------------------------------------------------|
33. | . . . . . 11 3 5 |
34. | . . . . . 12 1 4 |
35. | . . . . . 12 2 4 |
36. | . . . . . 12 3 11 |
|-------------------------------------------------------------|
37. | . . . . . 13 1 20 |
38. | . . . . . 13 2 17 |
39. | . . . . . 13 3 14 |
40. | . . . . . 14 1 2 |
|-------------------------------------------------------------|
41. | . . . . . 14 2 10 |
42. | . . . . . 14 3 10 |
43. | . . . . . 15 1 4 |
44. | . . . . . 15 2 5 |
|-------------------------------------------------------------|
45. | . . . . . 15 3 5 |
46. | . . . . . 16 1 15 |
47. | . . . . . 16 2 10 |
48. | . . . . . 16 3 7 |
|-------------------------------------------------------------|
49. | . . . . . 17 1 5 |
50. | . . . . . 17 2 5 |
51. | . . . . . 17 3 5 |
52. | . . . . . 18 1 38 |
|-------------------------------------------------------------|
53. | . . . . . 18 2 27 |
54. | . . . . . 18 3 25 |
55. | . . . . . 19 1 19 |
56. | . . . . . 19 2 18 |
|-------------------------------------------------------------|
57. | . . . . . 19 3 25 |
58. | . . . . . 20 1 2 |
59. | . . . . . 20 2 4 |
60. | . . . . . 20 3 4 |
|-------------------------------------------------------------|
61. | . . . . . 21 1 6 |
62. | . . . . . 21 2 6 |
63. | . . . . . 21 3 7 |
64. | . . . . . 22 1 11 |
|-------------------------------------------------------------|
65. | . . . . . 22 2 18 |
66. | . . . . . 22 3 21 |
67. | . . . . . 23 1 24 |
68. | . . . . . 23 2 17 |
|-------------------------------------------------------------|
69. | . . . . . 23 3 17 |
70. | . . . . . 24 1 10 |
71. | . . . . . 24 2 7 |
72. | . . . . . 24 3 8 |
|-------------------------------------------------------------|
73. | . . . . . 25 1 23 |
74. | . . . . . 25 2 16 |
75. | . . . . . 25 3 11 |
76. | . . . . . 26 1 50 |
|-------------------------------------------------------------|
77. | . . . . . 26 2 45 |
78. | . . . . . 26 3 44 |
79. | . . . . . 27 1 37 |
80. | . . . . . 27 2 31 |
|-------------------------------------------------------------|
81. | . . . . . 27 3 33 |
82. | . . . . . . . . |
+-------------------------------------------------------------+