524 



Marine Microbiology 



50 



40 



30 



20 - 



10 - 



u. 



o 

 § 30 



a. 20 



10 



10 



POINTS OBSERVED 

 LINE IS B-l-7 



o-» 



J L 



50 100 150 200 250 



NUMBER OF COLONIES PER FILTER 



B. 



CALCULATED 

 POISSON 

 CURVE 



c. 



A - B 



o-> 



50 100 150 200 



NUMBER COLONIES ON FILTER 



250 



Fig. 1. Standard error of the mean in bacterial colony counts where quad- 

 ruplicate membrane filters are prepared from the same dilution jar. Each 

 point in A is a mean of twelve to eighteen tests. The line drawn through 

 the points is curve B plus 7 percent. B is the calculated Poisson curve for 

 quadruplicate samples, constructed on the presumption that the standard 



