Sunday, September 16, 2007

Comments (and errors)

Some of us are computer literate, and some - are just a bit 'challenged', I think.

After being inundated with 'Anonymous' comments, reluctantly, we deleted that option - and apparently zapped all comments options. That was clever. So, Matt 5, read the book, and reinstalled 'Any Comments', but on scrolling down the blogger tool kit to verify the change, altered the next box to 'Allow No Comments' - at all. That was really clever. And not intentional.

About as good as the ISG's simple mathematical model which received an exclusive, professional brief peer review in our posting below.

Our modeler also challenged the ISG computer's maths on the incidence of New herd breakdowns, which were calculated as doubling 'every 4 and a half years'.

Incidence of New Breakdowns (7.21) on p148 - error on the first line
[The ISG quote] a compound IR of 15% - I’d be happy with that.
Compounding annually at 15% means it would double in 5 yrs not 4.5.
That’s out by 10%. A fairly big error straight off.

The maths: 1 x 1.15^5 = 2.01136

1 x 1.15^4.95 = 1.99735

Ten per cent is a lot to be adrift by - but hey, the ISG did describe their model as 'simple'.

Another 'error' was found by our eagle eyed contributers, in the recently published SE 3013 Pathogenosis project report. The stats on Gamma Interferon use within the trial we found odd, as was the conclusion of the mathematical calculations. Were some of the conclusions, including, possibly, this one, used to fuel a 'simple modeling exercise' too?

We quote from the point made to VLA on their figures for the IFN trial:
If 23 out of 96 tested negative to both of two tests, then logic dictates that at least 23 must have tested negative to either one of the two tests. So the figure of 9 in the last sentence quoted doesn't square with the earlier statement. But the higher figure of 30 reactors with unconfirmed bTB which tested positive could be correct. If so, 42% of reactors with positive IFN results but no confirmed bTB seems a large proportion.

And the answer confirmed our query:
"Thank you for identifying this error for which I am responsible: "23 out of 96 tested negative to both tests" should read " 6 out of 96 tested negative to both tests" . 23 out of 96 animals tested negative to either test".

So, 23 out of 96 (23.958 per cent) becomes 6 out of 96 (6.25 per cent)- an error of almst 18 per cent. Our modeler described the ISG's mathematical error of 10 per cent as 'fairly big". We can't begin to guess how he would react to a gaff of 17.708 per cent.

So when considering veterinary and epidemiological options based on these multi million £ research projects, readers would be wise to keep a firm handle on their brains and common sense, and if a conclusion looks odd, to question both the conclusion and the manner in which it was reached.


Matthew said...

Comment option looks OK, but what the **@!! have I pressed now - the blogger head page is in German(?)
"Sie k├Ânnen HTML-Tags verwenden"

I did say 'challenged' didn't I? Yup, I did. Time to ring the Boss.
Matt 5.

Anonymous said...

Just thought you'd been 'badgered'by you know who!!!

Matthew said...

Anon: 9.00
Hmm. Is our Trevor hibernating? A bit early we would have thought.

Nope, we suspect a cadged quote from Napoleon may be more to the point. It goes something like;

"Never interrupt your enemy when he is in the process of making a mistake".
We hear that the Trust are on a EU wide cash-crop grab, following the begging bowls which were out in the UK this spring. And we smell 'injunction'.

Farmers would be well advised to ignore the diminutive professor's upsidedown, in/out, roundabout off the cuff remarks in the RBCT report, and look hard at the Bern Convention for guidelines on any industry led 'strategy' on badger control.