The Spearman–Karber method was
used when intermediate mortality percentages (between
0 and 100%) occurred in the test dilutions but
the data did not fit the Probit model. The Trimmed
Spearman–Karber method was used when requirements
for Probit and the Spearman–Karber method
were not met but mortalities bracket 50%, the Probit
method when two or more of the observed proportion
mortalities were between zero and one and must
bracket 50%.