I have treated a species with two treatments:
salinity: five different concentrations
a pollutant (control and two different concentrations)
organisms grown with the two lowermost concentrations of salinity have been treated only with two concentrations of pollutant (control and the lowest one).
Trying to make a two-way ANOVA the software (PAST), as espected, replies that "one or more group is empty". I think it refers to the fact that the highest concentration of the pollutant has not been used with the two lowermost salinities*.
QUESTION: does an alternative test other than two-way ANOVA exist to verify the possible statistical significance of the differences observed and that can be used with such cases where one or more groups are empty?
Many thanks in advance
*: it is not a mistake in th designation of the experiment. It could not be tested.