Table 2. Guidelines used in selecting LD₅₀ values from multiple sources of data.

Rule Number	Available LD50 Data	Application
1	Single "exact" value reported	Used unmodified in analysis
2	Single value reported but qualified as "approximate" or "greater than" (>)	Used unmodified in analysis
3	Multiple "exact" values reported	Arithmetic mean of all values used in analysis unless the difference between the lowest and highest values was greater than 10-fold and then the geometric mean is used
4	Multiple values reported but all qualified as "greater than" (>)	Highest value used in analysis
5	Values reported but qualified as "less than" (<)	Not used in analysis