A method comprising: receiving a dataset comprising (i) a plurality of images, and (ii) a set of classes associated with one or more objects in the images; selecting at least one image from the dataset; applying one or more transformations to the selected image, to create a set of transformed images, wherein each of the transformed images includes a representation of at least one of the objects; annotating at least some of the objects in the selected image and at least some of the transformed images, wherein the annotating comprises assigning each of the one or more objects to one of the classes; and calculating an ambiguity score with respect to at least one pair of classes in the set of classes, based, at least in part, on a number of times the annotating assigned a one of the objects to both of the classes in the pair.