Look out for intervention effects that are described as average differences. Average measures of effects can be misleading.
For effects that are measured on a continuous scale (e.g. Population size or chemical pollutant levels in water) the difference between the average in one intervention group and the average in a comparison group may not make it clear how many subjects (i.e. populations or water bodies) experienced a big enough change (e.g. in size or pollutant level) for it to be regarded as important.
REMEMBER: When effects are measured on a scale, it cannot be assumed that every subject has experienced the average effect of an intervention.