On 16/02/13 10:35, Arfa Daily wrote:


"PeterC" wrote in message

That is the problem. Telling if something is wrong is fairly easy -
it's not
'as it should be', but there are hundreds of ways that something can be
wrong and many different tests needed. There doesn't seem to be a test to
tell if it's right.

But surely, that is the point ? If it's 'wrong', it ain't 'right', and
if it ain't *right*, then it's not 100% beef or whatever. Yes, it would
be nice to know what the contaminant was, but not actually necessary to
know that it's there. More detailed testing would then no doubt, be able
to determine exactly *what* the contaminant was ?

Confirmation and denial are asymmetric. You can test a sample for beef:
if you find beef that does not prove it is 100% beef. You can prove it
is NOT 100% beef: test for something else, it only takes a trace to
disprove the 100% beef claim. The problem is what 'something else'
should you look for? If you suspect horse, then that it what you test
for, if pork that's another test, etc


--
djc