[evanb]

I should add that the negative portion of the answer may not be from sampling the small tail of the Video Length distribution, but is much more likely to be an artifact of how you calculate uncertainty. It might be better to find the median and go out some % in each direction asymmetrically. You can see that the Total Time is roughly flat and then peters out.

[evanb]

Actually, the negative portion could be from sampling the much more substantial negative tail of the Viewers distribution. Either way, constraints seem to be important!