In article <[EMAIL PROTECTED]>,
Jerry Dallal <[EMAIL PROTECTED]> wrote:
Find_Housing wrote:
"David Heiser" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
....................
I'm not sure that's your question for a few reasons. Your real question
seems to be about the actual bacterial concentration level in the bag,
not that it's 10 or 1000. If it's a liquid and the bacteria don't clump
(or else see Student's paper on haemacytometers--Bk, 5, 351-360), your
ability to estimate the concentration will be determined by the
uncertainty in your measuring instrument, that is, the measuring
instrument will determine how many samples you need to determine the
concentration to a particular precision. It would like testing for
something in your blood. We rarely require a pint because we might miss
the virus in a particular tube.
About 50 years ago, the question came up about estimating the
concentration of bacteria with a given relative error with a
given confidence. The method being used was to count colonies
on a screen.
In a paper of which I am a coauthor, the simple method was to
count until a given number of particles was observed, instead
of counting a specific amount. This turns out not to be too
difficult; we were told that it is easier than the other.
Now if instead of estimating, it was desired to test, if at all
possible a sequential procedure should be used.
