Peter It depends on what you are looking for. In Chile we have our first outbreak of american foulbrood two years ago. If you went for a 10% sampling of yards you easily couldn`t find any cells with simptoms, so we have to increase the sampling to 20% to be 95% confident that a yard was free of AFB. I guess Bob is rigth in the case of CCD, since you do not know what you are looking at, one would have to increase the size of the sample. -- Juanse Barros J. APIZUR S.A. Carrera 695 Gorbea - CHILE +56-45-271693 08-3613310 http://apiaraucania.blogspot.com/ [log in to unmask] **************************************************** * General Information About BEE-L is available at: * * http://www.honeybeeworld.com/bee-l/default.htm * ****************************************************