Table 2

Comparison of stability between instruments of three methods: A. internal self mean ratio; B. ratios based on an external assay; and C raw instrument data. Internal self mean (A) is the most reliable. Using external ratios, (2C) is a close second, and raw readings, (2C) show the greatest deviation between instruments.


Ratios N = 32 for all.
Mean z score
Median z score
Max z
Min z

A
Ratios on internal self mean





Rh. Sera 1:50
1.07
0.84
2.08
0.52

Rh. Sera 1:100
0.96
0.92
1.21
0.76

Rh. Sera 1:200
1.86
2.31
3.50
0.14

B
Ratios on real external mean (SRV/SFV mean and SFV/SRV mean)





Rh. Sera 1:50
1.70
1.82
2.50
0.50

Rh. Sera 1:100
1.44
1.44
3.83
0.27

Rh. Sera 1:200
16.38
11.97
49.47
4.59

C
Raw inter instrument comparisons





Rh. Sera 1:50
1.19
1.09
1.75
0.61

Rh. Sera 1:100
8.14
7.91
9.69
6.98

Rh. Sera 1:200
46.04
43.89
65.40
26.52

Hanley Theoretical Biology and Medical Modelling 2007 4:32   doi:10.1186/1742-4682-4-32