I have 4 groups that identify different research field (animal, plant, microbe and insect). Scientists were asked to indicate in which group they belong and they were allowed to indicate more than one group - i.e. a scientist can be both in "animal" and "microbe". We then ask scientists a set of questions about time spent on research activities. We would like to compare means across groups. Normally, I'll use ANOVA but in this case the four groups are not mutually exclusive. Can I use t-test comparing each group against the rest of the population, i.e. those in the Animal group against all others? Is that appropriate? Are there better methods? I currently use R for my analysis.