Does Length Matter?
Previous research has suggested that optimal video length for online activities should fall in the 6-9 minute range (Risko et al 2012; Guo et al 2014). Only one of the videos selected for this class was this short and the longest video was four times this recommended length. Comments on length tended to be uncommon in the feedback on each individual video (Fig 4 ), but the comment that homework assignments generally were too lengthy and time consuming was in the top 10 response categories on the end-of-quarter feedback (Fig 7 ). It is possible that the end-of-quarter surveys are a more accurate reflection of student perception given their anonymity; however, even in this format, complaints about length appeared in less than 12% of comments (n = 29/243).
Homework 3 is an interesting case on this point. It included two videos that totalled nearly 19 minutes and which were rated lowest among all videos in terms of academic engagement (Fig 6a ) and emotional engagement (Fig 6b ) and for which the homework assignments received more than 5 times the number of complaints as any other homework. Yet this assignment received no negative, and two positive, comments about length (Fig 4 ). Both of the homework assignments that included two videos received fewer complaints about length than their total run time would predict compared to other videos (Fig 4 ), suggesting that multiple short videos were more palatable to students than one video of the same total length.
Homework 4 is also an interesting case. This was the longest video assigned, and was also rather advanced in terms of content and terminology. This video received the most negative comments about length, but was on par with or lower than other videos for other negative comments. Additionally, this video was the second highest rated in terms of positive comments on the presenter and tied for third-highest taxon of interest. Consequently, even a long lecture-style video on a complex topic can be interesting to students if paired with an engaging speaker and a charismatic organism.