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Bad at Reading, Math and Correlation? PDF Print E-mail
Written by Steve Dittmer   
Friday, 13 May 2005
AFF Sentinel Vol. 2, #22

More Misrepresentation and Unfounded Claims

Last edition [which should have been labeled #22 not #2], we debunked R-CALF's claims that Canada's surveillance-testing program did not meet OIE standards. Now we'll examine a chart supposedly boosting their claims. Please note, we do not vouch for the accuracy of their chart numbers. We are just examining the numbers from the chart in their own report. .

R-CALF's report ("Inadequacy of Canada's BSE Surveillance Program) includes a table it claims was taken from a European Commission report on TSE testing in selected countries in 2003. R-CALF claims the table reveals inadequacies in Canada's testing programs. It also claims Canada's deficiency is particularly obvious when comparing the number of tests conducted as a percentage of each country's adult cattle population.

We took numbers from R-CALF's chart, organized them into three smaller charts and compared them to the number of BSE cases in each country to search for correlations.

Table 1

Total cattle population appears to be a poor predictor of BSE prevalence; Belgium and the Netherlands, with populations many times smaller than Poland, have almost the same number of cases. And Slovakia, with a population only 15 percent that of Japan has half as many cases. Slovakia has a tenth of the population of Poland and one-third as many cases. As for Canada, all of the countries in the chart except Denmark and Slovenia have more cases from a much smaller total population.

In the next table, Denmark tests the second highest number of "high risk" cases and has the smallest number of BSE cases. Belgium tests nearly the same number of high-risk cattle as Denmark yet has 8 times the number of BSE cases. Japan tests all slaughter cattle without breaking out high-risk cases, so in effect, one assumes they test a large number of high-risk cases and yet rank in the middle of the number of cases found.

Table 2 and 3 including graph
The charts and our accompanying graph of the last chart show there is poor correlation between percent tested and number of BSE cases.

R-CALF also claims the chart numbers reinforce their call for Canada to begin testing "hundreds of thousands of cattle," including normal cattle slaughter. Since one of the lowest testing rates (Poland) shows the highest number of cases in their data, and two of the highest rates (Denmark and Slovenia) produced the lowest number of cases, we can't see any such reinforcement. None of the other numbers seem to bear out R-CALF's contentions. The charts would instead seem to indicate that the OIE has devised a formula and procedure that does a good job of determining the prevalence levels without having to test everything that moves.

R-CALF's report also contains the following statement:

"Statistically, the detection sensitivity of a testing program is driven by the number of cattle tested per month, not the size of the herd."

Is R-CALF claiming that setting a testing sample size has no relationship to the size of the total herd population? That whether the national herd is 100,000 or 10,000,000, it is only the number of tests conducted that counts? That if 300 is the right number for 500,000, it's also the right number for 10,000,000? We don't buy that statistically, and it makes no common sense either.

It is also incorrect to say sensitivity is only driven by test numbers in a given month. That is much too short a time period for an animal disease with an incubation period of three to seven years or more. That is why OIE sets their numbers on a yearly sample total, not monthly.

This is apparently an attempt to make something out of Canada's detecting two cases within a few weeks of each other around the first of this year. Statistically, that is not significant when surrounded by a year prior with no cases and none since.

Once again, it appears the numbers mean something different to R-CALF than it does to others, including the world's foremost international authority on animal health diseases, the OIE. If one evaluates the actual numbers, the numbers R-CALF is pointing to in its own paper and OIE's recommendations - none of these factors call for the huge number of cattle that R-CALF claims should be tested.

Misrepresentation of facts, unfounded indignation and false implications are not helping the beef industry protect consumer confidence and grow market share.

We understand some of you are also having difficulty accessing files on R-CALF's Web site. Therefore, we are providing a link to the PDF of R- CALF's report through the AFF Web site.

Here is R-CALF's Position Paper on the supposed inadequacies of the Canadian surveillance program (PDF on AFF site). Needless to say, AFF does not endorse their opinions. We provide this as a convenience for our readers only.

Next time: No, we're not finished. There are more errors.

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Last Updated ( Saturday, 24 June 2006 )
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