Determination of 50% endpoint titer using a simple formula

Table 2 Calculation of virus titre in mice using the Spearman-Karber method

Log10 virus dilution	Mice
	Died	Inoculated
-1	10	10
-2	10	10
-3	10	10
-4	10	10
-5	10	10
-6	6	10
-7	1	10

x₀ = 5; d = 1; log₁₀ of 50% endpoint dilution = - [5 - ½ + 1 (17/10)] = -6.2; 50% end point dilution = 10^-6.2; the titre of the virus = 10^6.2 LD₅₀/mL.