"David Heiser" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>... > Findamental is how well is the medium mixed. 10 bacteria makes sense if the > medium is truely homogeneous in all other constituents. The problem then is > the classic "balls-in-an-urn", since a bacterium is a finite particle, and > everything else is not a particle. If the medium is a gel, then the issue is > primarily one of homogenaity, and you have to take many more samples. One > then gets involved in a designed experiment involing three dimensional > sample locations. > > David Heiser
Thank you David. It's liquid, not gel. I am trying to readress the question as follows: The question is now "how to distinquish a bag that is 1000 bacterial per ml from a bag that is 10 bacteria per ml? How many samples of 1 ml should be taken out of a 60 ml bag? (0.9 power and 0.05 level of significance) Any way to estimate the variance? Aron . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
