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Animals avoid GM food
On 19 Aug 2003 10:18:51 GMT, Brian Sandle
wrote: Torsten Brinch wrote: On 18 Aug 2003 22:44:13 GMT, Brian Sandle wrote: [quoting:] These reports from farmers and seed dealers can easily be dismissed as anecdotal evidence from which no conclusions can be drawn. Indeed. And that will remain the case unless anecdotes are followed up by scientific studies of the matter. E.g. Shawn S. Donkin, Ph.D. Animal Sciences Department, Purdue University, fed corn/cornsilage to 16 dairy cows. 8 cows were fed from Bt corn, and 8 from a near isogenic line of non Bt corn. Average dry matter intake was 52.7 and 55.9 lb/d, for Bt and non-Bt respectivley (SE=1.12, p=0.06), average milk yield was 84.2 and 86.9 lb/d, (SE=1.20, p=0.15). Curiously the author concludes that his results show no differences. http://www.agry.purdue.edu/ext/forag...y_fed_spec.htm p=0.15 means that there is 15% chance that the result is spurious. No,no, you can't conclude like that. But, it is a common misunderstanding of p-values. p=15 means there is 15 % chance of observing a spurious difference of the observed magnitude or larger, -if- the situation is such that any difference observed will be spurious, i.e. when reality is that there is no difference. This is really a non-experiment on purpose I would say. The number of subjects has been kept down to 8 pairs so it is really impossible to get the p=0.05 needed to conventionally say you have significance. I couldn't be harsh as that. But of course, if a relatively few more animals had been used in the experiment, and the same difference had been observed in e.g. avg. dry matter intake between groups, that difference would have been considered significant when tested at the p=0.05 level. Once you have set up the experiment I think that would be the major cost and going to 16 pairs would have allowed the required significance and not cost much more. I am not sure that is true. Rather I should think the cost of the present experiment would be very significantly related to the number of animals. I mean, these are big animals, cows, they are not fed, kept and housed cheaply. If they were mice or rats, I would tend to agree. |
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