The observed efficiency of plating (e.o.p.) is defined as the ratio of two plaque or colony counts and is in practice subject to substantial sampling fluctuations. The true e.o.p. is here defined as the ratio of the underlying mean values, of which the two counts are Poissonian estimates: thus, when the number of counts on each plate is assumed to increase indefinitely, the observed e.o.p. converges in probability to the true e.o.p. A contour map is provided, by means of which one may rapidly determine, for any given pair of counts in the range 50 to 1000, an interval which will in 95 % of all cases contain the true e.o.p.


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  1. Ellis E. L., Delbrück M. 1939; The growth of bacteriophage. J. gen. Physiol 22:365
    [Google Scholar]
  2. Finney D. J. 1952 Statistical Method in Biological Assay London: Charles Griffin and Co. Ltd;
    [Google Scholar]
  3. Fisher R. A., Thornton H. G., Mackenzie W. A. 1922; The accuracy of the plating method of estimating the density of bacterial populations. Ann. appl. Biol 9:325
    [Google Scholar]
  4. Irwin J. O. 1938; A note on the standard error of the survival rate of bacteria in blood-bacterium mixtures. J. Hyg., Camb 38:748
    [Google Scholar]
  5. Kendall M. G., Stuart A. 1961 The Advanced Theory of Statistics. IIILondonCharles Griffin and Co. Ltd
    [Google Scholar]
  6. Meynell G. G., Meynell E. 1965 Theory and Practice in Experimental Bacteriology Cambridge University Press;
    [Google Scholar]
  7. Miles A. A., Misra S. S. 1938; The estimation of the bactericidal power of the blood. J. Hyg., Camb 38:732
    [Google Scholar]
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