  We compare the efficacy of animated and small multiples variants of
scatterplots on mobile phones for comparing trends in multivariate datasets.
Visualization is increasingly prevalent in mobile applications and mobile-first
websites, yet there is little prior visualization research dedicated to small
displays. In this paper, we build upon previous experimental research carried
out on larger displays that assessed animated and non-animated variants of
scatterplots. Incorporating similar experimental stimuli and tasks, we
conducted an experiment where 96 crowdworker participants performed nine trend
comparison tasks using their mobile phones. We found that those using a small
multiples design consistently completed tasks in less time, albeit with
slightly less confidence than those using an animated design. The accuracy
results were more task-dependent, and we further interpret our results
according to the characteristics of the individual tasks, with a specific focus
on the trajectories of target and distractor data items in each task. We
identify cases that appear to favor either animation or small multiples,
providing new questions for further experimental research and implications for
visualization design on mobile devices. Lastly, we provide a reflection on our
evaluation methodology.
