Happy new year. not least to the folks at the homeopathy4health site . They are jubilant about a “proof” that homeopathic dilutions could produce effects. albeit only on wheat seedlings. But guess what? After some questioning it was found that they hadn’t actually read the paper. Well I have read it, and this is the result.
The paper is “A Biostatistical Insight into the As2O3 High Dilution Effects on the Rate and Variability of Wheat Seedling Growth”. Brizzi,
Lazzarato, Nani, Borghini, Peruzzi and Betti, Forsch Komplementärmed Klass Naturheilkd 2005;12:277–283
The authors compared these treatments (30 seedlings each).
- C1, C2, C3 (untreated water p.a. Merck, control);
- WP (potentized water p.A. Merck) 5x, 15x, 25x, 35x, 45x;
- AD (diluted arsenic trioxide) 10–5, 10–15, 10–25, 10–35, 10–45;
- AP (potentized arsenic trioxide) 5x, 15x, 25x, 35x, 45x.
The allocation of seedlings to treatments was stated to be blind and randomised. So far, so good.
But just look at the results in Figure 1. They are all over the place, with no obvious trend as ‘potency’ (i.e. dilution) is increased. The
results with homeopathic arsenic at 45 days (the only effect that is claimed to be real) is very little different from the that of shaken water (water that has been though the same process but with no arsenic present initially).
For some (unstated) reason the points have no standard errors on them. Using the values given in Table 3 I reckon that the observation for AP45 is 1.33 ± 0.62 and for the plain water (WP45). it is 1.05 ± 0.69. The authors claim (Table 3) that the former is ‘significant’ (with a profoundly unimpressive P = 0.04) and the latter isn’t. I can’t say that I’m convinced, and in any case, even if the effect were real, it would be tiny.
Later the authors do two things that are a very dubious from the statistical point of view. First they plot cumulative distributions which are notoriously misleading about precision (because the data in adjacent bins are almost the same). They then do some quite improper data snooping by testing only the half of the results that came out lowest. If this were legitimate (it isn’t) the results would be even worse for homeopaths, because the difference between the controls and plain water (WP45) now, they claim, comes out “significant”.
Homeopaths claim that the smaller the dose, the bigger the effect (so better water down your beer as much as possible, making sure to bang the glass on the bar to potentise it). I have yet to see any dose-response curve that has the claimed negative slope. Figure 1 most certainly doesn’t show it.
Of course there is no surprise at all for non-homeopaths in the discovery that arsenic 45x is indistinguishable from water 45x.
That is what we have been saying all along.