  Physics education research on explanatory videos has experienced a boost in
recent years. Due to the vast number of explanatory videos available online,
e.g. on YouTube, finding videos of high explaining quality is a challenging
task for learners, teachers, and lecturers alike. Prior research on the
explaining quality of explanatory videos on classical mechanics topics has
uncovered that the surface features provided by YouTube (e.g. number of views
or likes) do not seem to be suitable indicators of the videos' explaining
quality. Instead, the number of content-related comments was found to be
statistically significantly correlated with the explaining quality. To date,
these findings have only been observed in the context of explanatory videos on
classical mechanics topics. The question arises whether similar correlations
between the explaining quality and YouTube surface features can be found for
videos on topics that are difficult to access visually and verbally, for
example from quantum physics. Therefore, we conducted an exploratory study
analyzing the explaining quality of N = 60 YouTube videos on quantum
entanglement and tunnelling. To this end, we made use of a category-based
measure of explanatory videos' explaining quality from the literature. We
report correlations between the videos' explaining quality, and the surface
features provided by YouTube. On the one hand, our results substantiate earlier
findings for mechanics topics. On other hand, partial correlations shed new
light on the relationship between YouTube's surface features and explaining
quality of explanatory videos.
