Forget Westlake’s symmetrical CI [General Statistics]
❝ […] It just does not strike me as being connected to the real world in any meaningful way
❝ Quite possible it made sense to somebody. At some point. Perhaps. Or maybe not.
I think it’s crap. I heard about it in the very early 1980s, when one of our sponsors suggested to report it as “additional information”. I said that’s rather “subtractive information” but he insisted. Life at a CRO is hard. A quote from the paper:*
This author's experience with bioequivalence trials suggests that most clinicians tend to make their equivalence statements in a symmetrical manner, stating, for example, that if the absolute (or possibly proportional) difference between µn and µs, is less than some specified value, then N is therapeutically equivalent to S and if not, doubt as to therapeutic equivalence exists.
❝ I wonder what the figures will look like for a drug which proves to be BE but with 1.00 not part of the conventional 90% CI?
I don’t understand. This is exactly my example above (BE, but 1 not within the conventional CI). Can you help my little brain?
Our 2,2,2 reference data sets in Phoenix/WinNonlin 6.3 (dropped in v6.4):
90% CI WL’s 90% CI
A 90.76 – 99.62 91.76 – 108.24
B 51.45 – 98.26 55.45 – 144.55
C 39.41 – 87.03 43.32 – 156.68
D 51.45 – 98.26 55.45 – 144.55
E 55.71 – 151.37 53.52 – 146.48
F 93.37 – 106.86 93.26 – 106.74
G 88.46 – 95.99 89.26 – 110.74
H 86.81 – 100.55 88.27 – 111.77
BTW, sometimes it is not possible to compute WL’s CI (see the paper).
- Westlake WJ. Symmetrical Confidence Intervals for Bioequivalence Trials. Biometrics. 1976;32(4):741–4. doi:10.2307/2529259.
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Science Quotes
Complete thread:
- IC90 vs IW90 Netzolin 2015-01-05 19:06 [General Statistics]
- Forget Westlake’s symmetrical CI Helmut 2015-01-06 01:43
- Forget Westlake’s symmetrical CI ElMaestro 2015-01-06 14:38
- Forget Westlake’s symmetrical CIHelmut 2015-01-07 00:41
- My mistake ElMaestro 2015-01-07 05:01
- My mistake nobody 2015-01-07 12:16
- My mistake ElMaestro 2015-01-07 05:01
- Forget Westlake’s symmetrical CIHelmut 2015-01-07 00:41
- Forget Westlake’s symmetrical CI ElMaestro 2015-01-06 14:38
- Forget Westlake’s symmetrical CI Helmut 2015-01-06 01:43